ee aod F URTHER LIMNOLOGICAL OBSERVATIONS ON THE - FINGER LAKES OF NEW: YORK 3:0 9:52 45, #4: + 2: +: By Edward A. Birge and Chancey Judy From BULLETIN OF THE BUREAU OF FISHERIES, Vol. XXXVII, r9i9=20 2 yeument Now 905 Bas ers) Shere ok ek dash he lh Tecwed Octobera, 1921 " ey LIBRARY ANNEX - PRICE, 10 CENTS “Sold only by the Superintendent of Documents, Government Printing Office, Washington, D, c. | WASHINGTON +2 5) xg) GOVERNMENT PRINTING OFFICE = 92: 0 2220105 : 1921 FURTHER LIMNOLOGICAL OBSERVATIONS ON THE FINGER LAKES OF NEW YORK : : - : By Edward A. Birge and Sans ce From BULLETIN OF THE BUREAU..OF ‘FISHERIES, Vol. XXXVII, 1919-20 Document No. 905 : 3: 3 & fos so 5 2 : 2: : : : : Issued October8, 1921 PRICE, 10 CENTS Sold only by the Superintendent of Documents, Government Printing Office, Washington, D.C. WASHINGTON ; : : : : : GOVERNMENT PRINTING OFFICE : : : 3:0: 9:0: 0: 3: : 192% : Rea Qu 48 Bola 300043 CONTENTS. & Page. THPOD UCI ON as aie dione aitalaa a rma oink Marmaris eine e Hae Ban enaiedvenndaeracace.oiyeaversbaunine audee RAGIN 21 Temperatures and heat budgets. ............ 00. c cece eee nee eee eee enn e eens eacasserei 2I1 Surface and bottom temperatures. ........... 0... c cece cee eee eee nee eontvavesatesdr Boa 212 Thermal, regions i csccosd ve nesaneney ans we naadineead ame uleh witless Jose) spn Siatetuentgeanaswarets sees 213 Summer’ heat incomes: ea ys.ceavticese eer nae ends oA eeaenes Ss FA LORE eee eee a Eee setshacaes 2r5 Distribution of heats :cxseceeacysdoeee a gemseecacses eAeReRTORTN DELS eae es EE eEEE EM ballasts ch avatans 218 Direct WOrkisacciatekiiens Gaagemeis sass arm Rey aga No Mads eee ee REESE tomes 219 Distrib tited, Works 5:5 sacs ice vcsciss ausceupieasosca iererddvdhnudesnmibiace do meeeia nite jorone iene A Nandita sano as rete 221 SEED EL ACEO I (CHEN ES is sats fcsce. costs execuiee tela dilate atetranar cs ScdUINaNmin ais neh cb taidysadacReinnes m oalundnneansyante SETS 221 Heat and work as measured at depth...... 0b cece teen een enn enes 222 JADSOrptiOn Of SUIS CHET RY ioe tiie sateen eeancienatenstasess enact Mio ine Mlle auncbe Aeclaidi’y Sone ile udherasnneea aly 223 Work: of thé: Suni iitt disttibiting Neat. 05 csccncsvirnnd tings var ctvace ont atapyedtawalecn ek Maw a-ha lb anes Se 232 Ph ati Rt OH Sse Soseg isis aeegrevene irises encanta ad Wc ae cucldca han NR RUN eeeKaeel giao Y iah dain Avenger 235 Methods aise taeesctgeeecrotonend cae aeons pe ciseeee wer achit tascam ieee cine Ra CERDaccunned Te 235 Net plankton’ cis cccnew nay eugene gaindlennewan ise Shek e ea Gimaaweoanant aca tenable 236 Phytoplankton. + so.c001 cones utianeesneees es ifiQh seta avenge anise earaes sx HE8 236 Zooplankton ycvassu9 ea cahanvawgerawsoatis o 1 ve Reena eeeMeaee tart ENTER ERENE NET OS 236 Nannoplankton vececssesn ss cs davaneendeaeaenaes bee Houses eed ate PAA eee 24 Plankton tables). << jcescnudanadierarn Sst baits erat kid Ss souipnain raya wdyaiesa\ goku doe oid egustieatnadescatitenracsiqda aed 243 Botton: fatina ic. 2 scan eects CA Osa chce iS nua cueat actin Sid auiseudcnatios andnctursaualtad A dabaysvtidud Waritatae ee 250 TACHA tr CLC hs sy ach ices ase avg pba svat cae a cGen cave) ase bb ase cgeaed oh cpac vara AeaUR NNN Meare ina ae 252 210 FURTHER LIMNOLOGICAL OBSERVATIONS ON THE FINGER LAKES OF NEW YORK. & By EDWARD A. BIRGE and CHANCEY JUDAY, Wisconsin Geological and Natural History Survey, Madison, Wis. & INTRODUCTION. In 1910 and 1911 the U. S. Bureau of Fisheries enabled the authors of the present paper to spend some weeks in the study of the Finger Lakes of New York. The results of this work were published in the Bulletin of this Bureau for 1912 (Birge and Juday, 1914). In this expedition there were applied to the study of the New York lakes methods that had already been tried on the lakes of Wisconsin, which are much smaller and shallower than those of New York. The resulting report dealt with the hydrography of the lakes, their temperatures and heat budgets, their content of dis- solved gases, and their net plankton. Since that study was made, the Wisconsin survey has increased the scope of its observations on lakes. In particular there has been devised and used extensively a new instrument, the pyrlimnometer, designed for measuring the transmission of the sun’s radiation through the water of a lake; numer- ous determinations of the weight of the individual members of the net plankton have been made; an elaborate study of the nannoplankton, both numerical and quantitative, has been completed; and it is now possible to make a rough correlation between count and weight of both net plankton and nannoplankton. The Bureau of Fisheries authorized a second expedition to the New York lakes in July and August of 1918, in order to apply these newer methods to them. The following paper reports the results of the observations. The authors are indebted to Hobart College, Geneva, for the free use of its labora- tories during their stay on the lakes, and to Prof. E. H. Eaton, of the same college, for unwearied assistance in their work. Much of the success which was reached. was due to this aid. All recorded series of temperatures between 1911 and 1918 were taken by Prof, Eaton, as also were those taken after August 1, 1918. This report comes from both of its authors, as was the case with their former paper on the same subject. Mr. Juday, however, has prepared the part which deals with the plankton and Mr. Birge that. which relates to temperatures and transmission of radiation. TEMPERATURES AND HEAT BUDGETS. The temperatures of the Finger Lakes were discussed in our former paper (Birge and Juday, 1914, pp.: 546-575), and it is untiecessary to repeat what was said there. Addi- tional observations have been. made and the discussion can be enlarged, therefore, at certain points.. aii 212 BULLETIN OF THE BUREAU OF FISHERIES. Table 1 shows the dates at which series of temperatures have been taken for usein computing the summer heat income. A five-year mean of August temperatures may be obtained for Canandaigua and Cayuga Lakes and a four-year mean for Seneca Lake. Additional observations are not likely to make essential changes in the results thus obtained. SURFACE AND BOTTOM TEMPERATURES. Observations of the surface in August and early September show in Canandaigua Lake a mean of 21.4° C., ranging from 20.7 to 21.7°; in Cayuga Lake the mean is 21.1°, ranging from 19.8 to 22.6°; in Seneca Lake, 20.4°, ranging from 20.0 to 21.1°- These must not be taken as the maximum surface temperatures, which undoubtedly are likely to come earlier in the season. Seneca Lake was visited on July 24, 1918, in the after- noon of a clear, hot day and at the close of a hot and windless period. The surface temperature in water 40 m. deep was 25.0° C. A heavy shower with violent squalls occurred later in the afternoon. The surface temperature on July 25 was 20.8° and there was a marked rise of temperature above that of the 24th at all depths between 5 and 30 m. TABLE 1.—DaTES OF TEMPERATURE SERIES: SURFACE, BOTTOM, AND MEAN TEMPERATURES. Lake and date. Surface. | Bottom. | Mean. Lake and date. Surface. | Bottom. | Mean. CANANDAIGUA LAKE. CAYUGA LAKE—continued. "ey °C. °¢. °C: *€. °C, Aug. 20, r910 21.7 5.4 11.05 |] AUG. 16, ITZ... e cece seer neers 22.6 43 9. 44 Sept. 4, r91r..... wad 20.7 43 10.02 |} AUg. 30, IQT8.... eee eee eee 22.0 4.2 9. 66 Aug. 27, 1914.. iat 21.6 45 10. 11 Aug. 31, 1916. . 21.6 5.0" rx. 57 | Meatieics ia csccciinse acne 2I.1 4.2 9. 43 July 27, 1918. . white 23.1 51 1r.9r |}. Sept: 3; 1978.55 escasenesereeves 21.5 5.0 II. 42 SENECA LAKE. Meat} 205.058 Sesgatetnes 21.4 48 10.95 |} AUG. 3, IQTO.... cee eee eee eee 20.2 4.2 791 Sept: 2) COLTsssiscicewate os deeuig 20.0 4.0 7.34 CAYUGA LAKE. Sep te. 54: TQ TA ecescieisisieiniwions via oie praise 2I.t 4.0 8.27 AUg. 29, 1918.....- 2. cece ee eee 20.8 4.0 8.07 gue EK, EQTOvecsaisenicmaiiovaeinens 19.8 43 9. 24 EB, TOME: sos iaasadauaraiaterae 20.0 4-1 8.93 Meatiicccsncdedrebeics weneaies 20. °! F Sept. 4, 1914........00ee eee ee ee 21.4 4t 9. 65 4 ee us Bottom temperatures average 4.8° C. in Canandaigua Lake (84 m. deep), ranging from 4.3 to 5.4°; in Cayuga Lake (133 m.) they average 4.2° with a range from 4.1 to 4.3°; in Seneca Lake (188 m.) the mean is 4.05° and the range from 4.0 to 4.2°. The reading was 4.0° in three of the four series. In most of these cases the observations were made with a Negretti and Zambra deep- sea thermometer divided to 0.5°. Such an instrument gives approximate but not very exact results. In 1918 the attempt was made to ascertain whether the water of Seneca Lake might not be below 4.0° C. at the bottom. The temperature of maximum density is lowered by pressure, as pointed out by Hamberg (1911, pp. 306-312). Since the depth of Seneca Lake is 188 m. the pressure at the bottom is about 19 atmospheres, and maximum density would be reached between 3.3 and 3.4°. A special thermometer was used, ranging from — 2.0 to + 14.0° and divided to 0.1°. This instrument read exactly 4.1° when at the temperature of the surface water, 19.3°. Correction for the expansion of the mercury. shows that the true temperature at the bottom was 3.88° and, therefore, below 4.0°, though decidedly above the temperature FINGER LAKES OF NEW YORK. 213 of maximum density for the depth. Hamberg (loc. cit.) quotes examples of similar temperatures from Lakes Ladoga and Mjésen. It is worth noting that the temperature in both these lakes at the depth of 190 m. was between 3.8 and 3.9°. The observations of Huitfeld-Kaas (1905, p. 4) in Mjésen give temperatures at 200 m. which rise as high as 4.1° in November and as low as 3.65 or 3.75° in April and May. At the bottom, 400 m. or more, 3.60 and 3.75° were Sa: 0 20: found. At this depth the tempera- ° rR ture of maximum density is slightly ™ : ra above 3.3°. o=3=3= It is very probable that the temperature of Seneca Lake, record- ed in 1910 as 4.2°, was really close to 4.0°, and that all readings of 4.0° at the bottom indicate temperatures as low as 3.8 or 3.9°. It is not worth while, however, to apply anestimated . < correction to these readings. There ba is no reason to believe that the bot- 7 eo 7 tom temperature of Cayuga Lake is / a below 4.0° in late summer. FA A r \ ON a RSet. ols J ‘diana od THERMAL REGIONS. S| 20 | Table 2 shows the thermal / Hf regions of the several lakes. The al epilimnion of Canandaigua Lake was 11 or 12 m. thick; the thermocline Wh was 4 to 8 m. thick, averaging 6 m. i i In Cayuga Lake the epilimnion was 13 to 15 m. thick and the thermocline 4 to 5 m. thick. There was more variation in | Seneca Lake. The epilimnion was I | 15 to 19 m. thick and the thermocline 4to6m. On August 1, 1918, the epilimnion at Hector Point was only rom. thick; on August 29, at Kashong, it was determined at 20m. But since Kashong is near the north end of the lake and the readings were taken on the day following a hard south wind, the epilimnion was no doubt thicker there than observations at the center of the lake would have shown. In computing gains of heat, therefore, the thickness of the epilimnion for 1918 was taken as 15 m. On July 24, 1918, at the north end of the lake in 40 m. of water the epilimnion was only 7 m. thick. This was at the end of nine days of hot and calm weather and is an exceptional condition. ‘The thickness of the epilimnion rapidly increased to 14 or 15 m. in the course of the following week and was subject to considerable fluctuations. so Fic. 1.—Curves of mean temperature to 34m. depth. A, Canandaigua Lake; B, Cayuga Lake; C,Seneca Lake. (See Tabie 1, p. 212.) 214 BULLETIN OF THE BUREAU OF FISHERIES. TABLE 2.—DISTRIBUTION OF SUMMER Heat INCOME TO THERMAL REGIONS OF LAKES. [Nore.—Mean is derived irom mean temperatures. Extent=vertical thickness of region in meters; R. ‘T.=reduced thickness of region, i. e., the thickness in meters of the region when reduced to the area of the surface of the lake. It is computed by dividing the volume of the stratum expressed in meters by the area of the surface of the lake expressed in square meters; T=gain of heat above 4.0°, i. e., the summer heat income expressed in degrees centigrade; Cal.=gram calories per square centimeter of lake surface; P, ct.=per cent.] ‘ CANANDAIGUA LAKE. Ig10 : IOI Thermal region. Extent. | R. T T Cal, P.ct. | Extent.| R. T. T Cal, P. ct. o-12 10.0 16.8 16, 800 61.8 o-12 10.0 15.5 15, 500 66. 4 12-20 5.6 9.3 5, 200 19.1 12-20 5.6 9.2 | 5, 200 22.0 20-84 23.1 2.73 5, 200 19.1 20-84 23.1 1. 04 2, 400 11.6 Meanortotal....].........- 38.7 7.07 | 97,200 |... ceceeeefeeeeee eens 387] 5.99 | 23,200 |.......... 1914 1916 Thermal region. Extent. | R. T. Ty, Cal, P.ct. | Extent.| R. T. T. Cal. P. ct. Epilimnion.... O-Ir 9. 34 aI.o 15, 830 58.6 o-12 10.8 aI.2 17, 420 59.3 Thermocline. 11-18 5. OL 14.0 §, 010 18.6 12-20 5. 64 13.3 5, 270 17.9 Hypolimnion.. 18-84 24. 45 6.5 6, 160 22.8 20-84 23. 08 6.9 6, 680 22.7 Meanortotal....].......... 38.8 10. 96 27,000 |.vceeesessfecesves pis 39. 52 IX. 57 99370: |asisce ea vee 1918 Mean. Thermal region. Extent. | R. T. T. Cal, P.ct. | Extent.| R. T. ie Cal, P. ct. o-II * 9.34 20.7 15,610 54-3 o-Ir 9. 34 20. 8 15, 660 58.0 II-15 2.91 16.4 3, 560 12.4 I-17 7.18 15.9 4,970 18.4 15-84 26. 25 7 9, 600 33-3 17-84 25. 82 16.5 6, 350 23.6 Mean or total...... es asavbjotedebeieis 38.5 Il. 42 BO RTO) | Sciayaispajazaca aches iia pails 42. 34- 10. 95 26, 980 |........0 CAYUGA LAKE. 1910 IQIr Thermal region. Extent. | R. T. T. Cal. P.ct. | Extent. | R.T. TT. Cal. P. ct. Epilimnion.. ts ois 11.8 18.5 18, 300 64. 2 o-16 12.5 15.2 19, 000 Thermocline. . wee] 19-22 4-62 10.3 4, 800 16.9 wé-2r | 3.3 = a “ 300 ee Hypolimnion.......... 22-133 38. 3 I. 4 5,400/ 189 21-133 38.7 1.14 4, 400 16. 5 Meanortotal....].......... 54. 72 5. 26 BB) SOO: | sisiarhese aes aiNatea doveuee 54.5 4-94 26, 700 |.......... . 1914 1917 Thermal region. ; Extent. | R. T. T. Cal. P.ct. | Extent. | R.T. T. Cal. P. ct. o-I5 II.97 21.2 20, 624 66. 8 o-13 10, 56 21.0 17, 60. 15-20 3-35 16.7 4, 266 13.8 13-17 2.76 15.6 3 oe ro. i 20-133 39. 27 5.5 5,980 19. 4 17-133 Ig. 29 6.1 8, 542 28. & Meanortotal....J.......... 54-59 9. 65 BO} BIO: Pare rea ninle favetevaroronre’s 0 27.61 9.44 29,720 |... eee eeas 1918 Mean. Thermal region. R.T. T. Cal. P.ct | Extent.| R.T. T. Cal, P. ct. Il.97 20.4 19, 734 63.9 ors 11.9 20. » 538 a 2.70 14.0 2,716 8.8 15-20 3 a 14. i a ve a 39. 94 6.1 8, 460 27.3 20-133 39. 27 5.6 6, 309 2s Meanortotal....].......... 54. 61 9. 66 39 910 |..... tardies leant aaied 54. 59 9. 40 29, 480 |...... FINGER LAKES OF NEW YORK. 215 TABLE 2.—DISTRIBUTION OF SUMMER Heat INCOME To THERMAL REGIONS oF LakES—Continued. SENECA LAKE. ' a ae T910 IQII Thermal region. Extent. | R. T. T. Cal, P.ct. | Extent. | R.T. T. Cal. Pct. o-12 Ing 15.4 17, 700 53.8 ors 13.8 15.4 21, 200 7. 5 u I 12-20 6.2 10.2 6, 400 19.5 15-22 6.0 8.6 5» 200 17.5 Hypolimnion... 20-188 70.9 1.21 8, 800 ar.7 22-188 68. 8, 0. 47 3) 300 11.0 Meanortotal....].......... 88.6 372 325.900) ll soag sects aeauusmacirers 88.6 3-35 29,700 |oc.. ee ee ease 1914 1918 Thermal region. ae i . Extent. | R.T. Tv. Cal. P.ct. | Extent.| RT. T. Cal, P. ct. o-I9 16. 92 20.0 27, 000 71.2 o-rs 13. 60 20.0 22, 420 62.2 19-25 4. 83 13.9 4, 780 12.6 I§s-19 3.32 14.6 3,510 9.8 25-188 » 66. 85 49 6, 090 16.2 19-188 71. 68 54 10, 030 27.9 Mean or total..../.........- 88.6 8.27 B7P 870: | cisiteda sealant axe 88.6 8.07 | 36,060 ].......... Mean. Thermal region. Extent. | R. T. T Cal. P. ct. Epilirninn loan sciscisis'es sinittnienes ns vvieelaislatgaventea bales dadsqaislers bo dai Saeceaonvamanes ee ois 13. 60 19.8 23, 410 63.0 Thermocline iis scissicideeiivians os sglansayaarn tg ne Feidieeelapt ede eet aoa nagunamas 98 £6 4 15-20 4.13 14.8 4,450 13.1 PEYPOUMIION, socsi ria nemuewes ya eeHoaseeecs een pat omnaiaea ne amnatraansiade ma he esta 20-188 70. 87 5.2 8, 160 24.0 Meanor totalieves cxseunvas cageeeuss vi 2euesanss vevenneas taunmeuse vaalnnnas ¢ ee 88.6 $84 | 34,820 [rrcowerees SUMMER HEAT INCOME. The summer heat income represents the gains in heat of the water of the lake above the temperature of 4°. This notion was put forward in our paper on the New York Lakes (Birge and Juday, 1914, p. 562) under the name of “ wind-distributed heat.” In the following year (1915, p. 167) I proposed the name ‘‘summer heat in- come’’ for the same gains of heat, preferring a term which does not imply any theory as to the method of distributing such heat. For reasons discussed in the same paper (1915, p. 186) the summer heat income of lakes can be used as an index of their heat exchanges in much the same way as the annual heat budget. The heat income, like the heat budget, is stated in gram calories per square centimeter of lake surface. For the sake of brevity it is ordinarily stated as so many calories without adding in every case the qualifying terms. ‘The whole question of heat budgets and the methods of computing them is discussed in the paper already referred to (Birge, 1915). Table 2 shows the summer heat income of the three lakes concerned. Canandaigua Lake shows a mean income of nearly 27,000 cal./cm.’, ranging from 23,000 to more than 29,000 cal. Cayuga Lake has an income of about 29,500 cal., ranging from less than 27,000 to nearly 31,000 cal. The income of Seneca Lake is about 34,000 cal., ranging from less than 30,000 to nearly 38,000 cal. The smaller income of Canandaigua Lake is mainly due to the thinner epilimnion, which, in turn, is due to the smaller size of the lake and to the protection from wind afforded by its high shores. So far as area goes, Cayuga Lake is as well off as Seneca and its depth is ample to secure as large anincome. But while the epilimnion in both lakes is 15 m. thick, its reduced thickness is nearly 12 per cent less in Cayuga Lake than in Seneca. ‘This fact is due to the large extent of shallow water at the north end of the lake, which causes a corresponding reduc- 216 BULLETIN OF THE BUREAU OF FISHERIES. tion in the amount of heat as stated in terms of units of surface area. The upper 20 m. of these lakes contains 75 to 80 per cent of the total quantity of heat, and the reduced thickness of this stratum in Cayuga Lake is nearly 14 per cent less than in Seneca Lake. (See Table 3.) ‘The slightly higher temperature of the stratum in Cayuga Lake is not great enough to compensate for this difference in thickness (cf. Birge and Juday, 1914, p. 574). A longer series of years would undoubtedly change the figures stated above. But it is not probable that such a series would greatly alter them or that it would change the general relations of the heat income of the several lakes to each other. The smaller lake has the smaller income, largely because of its thinner epilimnion. Cayuga Lake has less heat than Seneca, largely because of the smaller ratio between maximum and mean depth. ‘The differences are not so great but that the series of budgets overlap, the largest heat income of Canandaigua being larger than the smallest of Cayuga, and Cayuga’s series overlapping in a similar way that of Seneca. The largest heat income in the series is that of Seneca in 1914, nearly 38,000 cal. Table 2 also shows the distribution of heat to the three thermal regions of the lakes. ‘The epilimnion contains about 60 per cent of the summer heat income, ranging from 53 to more than 70 per cent. ‘This stratum, together with its thermal depend- ency, the thermocline, contains from 70 to nearly 9o per cent of the heat. Thus in Seneca Lake, which may be nearly 200 m. deep, a surface stratum occupying little more than the upper one-tenth of the depth contains from three-fourths to nine-tenths of the heat accumulated from the sun during the season. Table 3 shows the distribution of the summer heat income by 10 m. intervals. It shows the same facts as Table 2 but in another form. It makes especially clear the small amount of heat which can be carried to considerable depths. In Canandaigua Lake, for example, the total quantity of heat transmitted below 50 m. during the season does not exceed the quantity delivered to the surface in one summer day; and even in the much larger and deeper Seneca Lake it does not exceed two days’ supply. TABLE 3.—DISTRIBUTION OF TEMPERATURES AND OF CALORIES OF SUMMER Heat INCOME. [NotE.—R. T.=reduced thickness of stratum in meters; T.= temperature in degrees centigrade; Cal. =calories of summer heat income, i. e., gain of heat above 4°; P. ct.=per cent of heat income in stratum.] CANANDAIGUA LAKE. . IgIo Igrr 1914 Depth in meters. R. T. as Cal. P. ct. T. Cal. P. ct. T. Cal. P. ct 0-10 8.56 21.2 14, 720 53-3 19.9 13, 610 58.2 211 14, 640 56.3 7.16 14.3 7,370 27.0 14.2 7, 300 31.5 13.6 6, 870 26.4 6. 43 24 2, 190 8.0 6.1 I, 350 5.6 2A 2, 190 8.4 5.71 6.2 1, 260 47 49 510 2.4 6.3 I, 310 5.0 4. 88 5.8 880 33 4.6 290 2 54 680 2.6 3. 65 5.6 580 2.3 45 180 +8 4.8 290 LI 1.90 55 280 I 4.35 70 3 46 110 +4 +53 5.4 70 +3 43 2O Jo ncncnacee 45 20 oT ee aneesese II. 05 27,350 100. 0 10, 02 23, 330 100. 0 10. 71 26, 110 100, 3 1916 1918 Mean. Depth in meters. R. T. i Cal. P. ct. T. Cal. P. ct. x, Cal. P. ct. OAO. esisawe nates 18.454 8. 56 21.4 14, 890 50.7 20.8 14, 380 50.0 20, a 9 14, oO 5 FOK8O eects snhine erin exe 7.16 14.9 7, 800 26.6 14.9 7, 800 27.1 14.4 a he a 2 ce 6. 43 8.6 3,420 11.6 8.9 3,150 Ilo 7.8 2, 460 9.1 5-71 6.6 1, 480 5.0 6.8 1, 600 5.6 6.1 I, 230 46 4. 88 5:9 930 3.2 5.9 93° 3-2 Bs 740 2.7 3. 65 5.5 / 550 19 5.6 570 2.0 5.2 430 16 1.90 5.3 250 8 5.4 270 Lo 5.1 200 5 +53 5.0 50 +2 5.3 7° +2 48 4° a isle Reiate ne IL. 57 29, 370 100, 0 IX. 42 28,770 100. 1 10. 95 26, 980 99. 9 FINGER LAKES OF NEW YORK. 3 217 TABLE 3.—DISTRIBUTION OF TEMPERATURES AND OF CALORIES OF SUMMER HEAT INcomME—Con. CAYUGA LAKE. ‘ IgI0 we : IQII 914 Depth in meters. R. T. Fr T. Cal. P. ct. Tr Cal. P. ct. i. Cal. P. ct. 8. 42 19. 2 12, 800 44.8 19.9 13, 400 40.8 21.3 14, 600 47-3 6. 88 | 17.7 9, 400 32.9 17. 9, 000 33-5 18,8. 10, 200 33-0 6.27 8.8 3, 000 10.5 8.2 2,600 9.7 9.6 3, 500 11.3 5.79 6.4 1,400 49 5.6 900 34 6.2 I, 300 4a 5.12 5.4 Joo 24 47 350 1.3 5.2 600 1.9 4 52 49 400 1.4 44 180 +7 4.6 290 “9 4.93 4.6 250 “9 44 140 “5 44 160 “5 3-60 45 190 +6 43 130 +S 43 90 +3 5. 89 45 290 1.0 4.2 120° “4 4-1 go 3 4.09 44 170 6 42 80 3 41 4o oi 54. 6 9. 24. 28, 600 |.......... 8.93 26, 900 does ae, 9. 65 30, 870 |.......... P I9I7 1918 Mean. Depth in meters. R. T. T Cal. P. ct. T. Cal. P. ct. T Cal. P. ct. 8. 42 21.3 - 14, 600 49.2 aur 14, 400 46.6 20.6 14, 000 ALS 6. 88 16.1 8, 300 28.0 16.4 8, 500 27.5 17-3 9, 100 31.0 6.27 8.8 3, 000 10. I 9.1 3,200 10. 4 9.0 3, 100 10. § 5.79 6.9 I, 700 57 71 1, 5.8 6.4 I, 400 48 5.12 5-7 880 3.0 6.3 I, 200 3-9 5.5 770 2.6 452 49 410 14 57 750 2.4 49 410 14 4.03 48 320 Li 5I 44° L4 46 260 9 3: 60 4s 180 6 47 250 8 45 160 5 5- 89 44 210 “7 45 290 +9 43 190 “7 4.09 43 120 4 42 80 A 42 go <3 = 54. 61 9. 44 29, 720 |.......... 9. 66 30,910: lia vautiiges 9. 40 29, 480 |.....006 se SENECA LAKE. 48 I9I0 IIL 1914 Depth in meters: R. T. tT. CaL P. ct. T Cal. P. ct. T. Cal P. ct. 9. 35 19.6 14, 600 44.4 19.6 14, 600 49. 5 20.3 8. 40 15.7 16, 2 10, 200 34-5 19.2 7. 86 8.7 23 2,600 8.8 Il 4 7.41 6.4 5.8 800 2.7 7.1 6.92 55 4.6 400 13 54 6.49 49 44 280 1.0 47 5. 89 4.8 43 160 +6 44 5. 52 4.6 43 160 -6 42 g. 82 AS 4.2 ates 4.0 12.14 42 41 4.0 5. 76 4.2 4.0 4.0 3. 22: 4.2 40 40 dete cedertse 7.7% 32,900 cao nia bits 7 34 29,600 |......5... 8.27 1918 Mean. Depth in meters. R. T. ae Cal. P. et. T. Cal P. ct. 9.35 20. 5 15,400 42.7 19.9 14,900 43.8 8.40 17.2 II, 100 30.8 17.1 10, 960 32.4 7. 86 9-9 4, 600 12.7 9.3 4, 200 12.4 74 6.8 2, 100 5.8 6.3 I, 700 5.0 6. 92 6.0 I, 400 39 5.4 940 2.8 6. 49 5.2 760 2.0 46 420 12 5. 89 44 230 +6 45 270 8 5. 52 4.3 160 +4 43 180 Ss 9. 82 4.2 190 8 4.2 260 8 12.14 4.1 120 +3 41 130 «4 5. 76 ees 4.0 40 ak 3.22 4.0 BO iasce's Savona sieieeiceieie we 7.84 34,020 |.......85 46104°—21——-2 218 BULLETIN OF THE BUREAU OF FISHERIES. DISTRIBUTION OF HEAT. The radiation from the sun which enters a lake is rapidly absorbed by the strata of water near the surface. Even in very clear lakes only 20 per cent of the total radiation passes the 1-meter level, and only about 10 per cent passes the 3-meter level. (See p. 228.) All of the warming of the deeper water and most of the warming of that which lies below the surface meter is due not to insolation but to mixture of warmer water carried down from near the surface. This mixture of warm surface water with the cooler water below is effected by the wind for all temperatures above 4°. It involves work against gravity, since the warmer water is lighter than the cooler. This work may be measured and may be conveniently stated in gram-centimeters per square centimeter of lake area. These facts were stated in our paper on the New York Lakes (Birge and Juday, 1914, p. 562). The principles underlying these ideas were later published as a special paper (Birge, 1916, pp. 341-391) and were applied to Lake Mendota. It was there shown that about 1,210 gram-centimeters of work per square centimeter of area are needed to distribute 18,400 gram-calories of heat per square centimeter of area through the waters of a lake 24 meters in maximum depth and 12.1 meters in mean depth. It is understood that in this statement the term “‘work’’ is not used in an exact sense; since in it are included both the action of the wind in distributing heat, which is properly work; and also the direct effect of insolation, which does not involve work. (See Birge and Juday, 1914, p. 574; Birge, 1916, p. 360.) This division of the distribution of heat between sun and wind is discussed later in the paper. For the present, however, the matter is discussed as though the entire distribution of heat were due to wind. TABLE 4.—TEMPERATURE (T) IN DEGREES CENTIGRADE AND GRAM CENTIMETERS (G. CM.) oF WorkK NECESSARY To DISTRIBUTE THE SUMMER HEAT INCOME. [Nore.—This table shows the “direct curve of work,” i. e., the work necessary to carry the warmed water from the surface to the stratum in question. It is stated in gram centimeters per square centimeter of surface of the lake.] CANANDAIGUA LAKE. Igto IQII 1914 1916 1918 Mean. Depth in meters. T G. cm. T. G. cm. Tv G. cm. T G. em. T G.cm. | T. G. cm. 236. 2 20.0 224.0 215 240. 8 2n.5 240. 8 aur 224.0 2I.1 224.0 582.0] 19.6 505.3 20.7 574.1 21.3 613.0] 20.6 568. 1 20.6 568. 1 630.7] 17.5 589. 5 16.9 539-3 17.8 612.4] 17.0 548.4] 17.5 589. 5 199. I 10.6 199. I 10. 2 176. 6 12,0 288. 3 12.5 309.6 | 11.2 235.5 100. 4 6.2 25.8 74 62.7 9.2 149. 8 . 8 191.9 8.2 100. 4 60. 8 5.4 13.7 6.9 56.5 8.0 106. 1 8.0 106. 1 ed 64.2 75.2 4.9 13.9 6.3 83.2 6.6 104.9 6.8 122.8 6.1 69.3 57.2 4.6 6.6 54 35-2 5.9 63.8 5.9 63.8 5-5] 39.6 42.0 4.5 4.0 4.8 10,0 5.5 36.0 5.6 42.0 5.2 24.0 22.3 44 I.2 4.6 37 5.3 17.4 54 19.8 5.1 12.4 6.7 4.5 “4 45 -8 5.0 3-3 5-3 5.8 4:9 2.9 Vie vas 2,022.6 |.......] 1,583.5 |...-.-.] 1,782.9 ].......] 2,235.8 |.......] 2,202.3 |....... 1,929.9 FINGER LAKES OF NEW YORK. 219 TABLE 4.—TEMPERATURE (T) IN DEGREES CENTIGRADE AND GRAM CENTIMETERS (G. Cm.) oF WoRK NEcESSARY TO DISTRIBUTE THE SUMMER Heat INcomE—Continued. CAYUGA LAKE. Ig1o Iglr 194 IQI7 1918 Mean. Depth in meters. ch G. om. f. G. cm: + G. cm. T. G. cm. t. G. cm. T G. cm. 19. 6 187.6 | 20.0 195.4 | 21.4 229.8 | 21.8 239.8 | 214 237.5 20.8 am5.3 19.6 488. 4 19.9 497.1 21.4 598. 2 20.7 554.9 | 20.8 560.7] 20. 540. 4 19.4 727,6| 19.6 745.3 | 20.9 864.4 | 18.8 674.7 | 19.3 718.8 | 19.6 745-3 16.0 603.6 | 14.9 503.4. 16.7 673.9 13.2 363.9 13.4 379.1 14.8 494.6 9.9 189. 6 9.0 137-9 | 11.0 264. 2 9.8 183.8 | 10.0 | 196. 1 9.9 89.6 7.8 95.0 6.9 56.0 8.0 105. 2 4 9°. 7 8.2 115.3 7 90.7 6.4 94.9 5.6 30.3 6.2 70.7 6.9 133-3 71 147-5 6.4 92.9 5.4 41.6 4.7 5.8 5.2 20.8 5:9 53.1 6.3 97.0 5.5 41.6 49 17.4 4.4 5.0 4.6 6.2 49 17.4 5-7 54.8 49 17-4 4.6 9.2 44 2.6 4.4 2.6 4.8 13.1 5.1 26. 2 4.6 9.2 4:5 5:4 4.3 2.7 4.3 2.7 4.5 5.4 47 12.1 4.5 4.0 4.5 10.6 BoD hase saa Beh, | oa de reese 44 5.3 4.5 10.6 4-3 5.3 44 72 Bie sats davdind Bk. les haccgemen 4:3 4.8 Asa! is oiaeanceeas Bod || eer-n wees a Rianite 2,478.10 |.......] 2,181.5 |.....-6| 2,838.7 [o..eeee] 253402 |o...eee] 2,555.7 [eee eee 2, 446. 3 SENECA LAKE. 1910 IQIr 1914 1918 Mean. Depth in meters, T G. cm. t G. cm T. G. cm. T G. cm. 7 G. em OSes s ta cawaeaeas oo 19.8 205.9 19. 7 203. 5 20.4 220, 2 20.6 226.5 20.1 213.0 5-IO..... 19. 4 552.8 19. 2 539-4 20.2 603. 0 20.5 626. 4 19. 8 579.6 IO-I5..... 17.8 718. 2 17.8 718.2 20,1 959. 4 20. 2 975.5 Ig. 2 863.0 15-20..... 13.3 457.8 14.0 526.3 18.0 996. 4 14.0 526.3 14.8 609. 4 20-25..... 9.3 i 8.0 112.2 13.4 585.5 IL 5 380. I 10. 6 296.8 25-30..... 7.9 6.3 44.9 9.4 237-5 8.2 8.0 132.7 3O-40.,... 6.4 5.8 67.6 71 195.0 6.8 6.3 109. 2 40-50..... 5.5 4.6 9.3 5:4 49.8 6.0 5.4 49.8 50-60..... 49 44 3-5 4:7 14.0 5.2 4.6 10. § 60-70..... 4.8 434, 3-8 4.4 3.8 44 4.5 7.6 7o-80..... 4.6 43 5.5 AD lccaatee cet 4.3 4.3 45 80-100 45 Be 2 lecegenasas BEO bsterguss eae 4.2 4.2 100-130... 4.2 Aid, lamsewsene.s AO: leaner esas 4.1 |. 4-1}. 130-150... ane 4.2]. (As OF leat sees AiO! |wexaaeycenis 4.0 |. 4.0]. T5O-188. 0... ee eee eee 4.2 AEG: |isccctasses sn 450 |passe canes 4.0 4.0 ore enerf) STO. |. ovewandes 2,234.2 |occeseeeee| 3,864.6 |.......00 a Sirisisieeaeee DIRECT WORK. Table 4 shows the distribution of heat for the lakes under consideration. The resuits of the computation only are given; the details of the method being quite similar to those illustrated in the paper before referred to (Birge, 1916) and also in Table 5, page 220, of this paper. Taking the means only it appears that in Canandaigua Lake about 1,930 g. cm. of work per square centimeter of the area of the lake are needed to. distribute about 27,000 cal. of heat through the water, the depth of which is 84m. In Cayuga Lake about 2,450 g. cm. of work distribute 29,500 cal. in water, the maximum depth of which is 133 m.; in Seneca Lake 2,880 g. cm. distribute 34,000 cal. in water the maximum depth of which is 188 m. The amount of work needed to carry the heat to the corresponding stratum of the several lakes varies with the loss of density of the water due to rise of temperature and with the quantity of water in the stratum. The latter factor is represented by the reduced thickness of the stratum. (See Table 3.) The first factor is the more 220 BULLETIN OF THE BUREAU OF FISHERIES. variable in these lakes, and to it are due most of the striking differences in the work required to warm the deeper strata: In the 30 to 4o m. stratum of Canandaigua Lake, for instance, it required about 70 g. cm. to put 1,230 cal. into place. In the corre- sponding stratum of Cayuga Lake it required 93 g. cm. to place 1,400 cal. The difference in calories is about 14 per cent, in work over 30 per cent. This is mainly due to the difference in loss of density. At 6.1°, the temperature of Canandaigua Lake, this is 35 points,’ and at 6.4°, the temperature of Cayuga Lake, it is 46 points, or over 30 per cent greater. Table 4 shows that a great amount of work is necessary to produce by mixture the high temperature of the upper strata; it shows also that an almost incredibly small amount of work is needed to carry considerable heat to great depths if only it involves but little rise of temperature. Note, for example, Seneca Lake, where 42 cal./cm.? of surface are transported to a mean depth of 55 m. for an expenditure of about 1 g. cm. On the other hand, in the corresponding stratum of Canandaigua Lake, each gram centimeter of work transports only about 18 cal. The difference is due to the much greater rise of temperature in the smaller lake—reaching 5.2° instead of 4.5° in Seneca Lake. TABLE 5.—DETAIL FOR SENECA LAKE OF THE Facts oF DisTRIBUTION OF MEAN SUMMER Heat INCOME. {Norg.—T.=temperature in degrees centigrade; 1-D=loss of density due to warming; RTXZ=factor, reduced thickness multiplied by depth. Direct=work done in behalf of stratum in question; Dist.=work done im stratum in question; Cal.= calories of summer heat income in stratum. All expressed in units per square centimeter of lake surface. See fig. 3, p. 229; also Birge, 1916, p. 349,355.) . Direct work. Dist. work, Depth in meters. T. =D. |RTXZ. Cal. in G.cm. | Cal. 0. 001853 1,624 ©} 2,874.4} 34,020 181g 1, 588 1 | 2,589.8 | 32,396 1815 1,555 2 | 2,323-3 | 30,808 1790 I, 530 3 | 2,074.5 | 29,253 1770 1, 504 4] 1,843.0] 27, 723 1770 1, 488 5 | 1,629.4] 26,219 1749 15447 6 | 1432-4] 24,73 1729 1,422 7 | 1,251.6 23,284 1708 1,382 8 | 1,086.7 21, 862 1708 1,366 9 937-1 20, 480 1688 1,357 Io 802. 5 19,114 1668 1,333 IL 682. 7 17,757 1628 1,316 12 577-5 | 16,424 1519 1,258 13 486.6 | 15,108 1491 1,241 14 410.1 | 13,850 1269 1,126 15 345-5 12,699 1030 996 16 292.5 II, 483 0844 896 17 249. 2 10, 487 0674 787 18 213-6 9) 59L 0475 648 19 184-3 8, 804 0328 2,653 20 159: 7 8,156 0124 1,560 25 78.9 5 503 0042 1,714 30 43-2 31943 0016 969 40 13-7 2,229 0003 485 50 4.6 1,260 e002 263 60 7 775 oO0or 165 70 +4 512 dia aietinenees 347 Bo +O 347 PSaaiwiied . 2,874.4 34s O20" fiers ks oe 25) Pacem aive eee 1 By a “point” is meant a decrease in density of one part per million. The density of water at 6.1 as compared wi at 40° is 0.999965. ‘The loss in density is, therefore, 0.000035 and this represents the loss in weight of the Tenrereiinee abe t 6.r°, and, therefore, is one factor in determining the work to be done in pushing it down into deeper and cooler strata. For con- venience in computation this factor is taken as a positive quantity and a whole number is stated as 35 points. (See Birge, 1916, D. 391. * Ts : FINGER LAKES OF NEW YORK. 221 DISTRIBUTED WORK. Table 4 deals with the direct curve of work. It gives for each stratum the amount of work necessary to convey the warmer and lighter water from the surface to the depth in question, assuming that the lower water has a temperature of 4.0°. In warm- ing all strata below that at the surface most of the work is performed in the strata above that for the benefit of which the work is done. If the work for each stratum is thus distributed to the several strata above it, we derive the curve of distributed work. (See Birge, 1916, p. 355). This is shown for the mean of each lake in Table 6 and for Seneca Lake in figure 3. The numbers for each stratum show how many gram centimeters are necessary to distribute through the stratum the heat retained in it and to convey through it the heat which goes on to lower strata. The table shows how shallow is the stratum which receives most of the work of the wind. More than 94 per cent of this work is expended in conveying the heat through the upper 20 m. of the lake. While the effect of the wind extends to the bottom, even in Seneca Lake, the work done in the deeper water is very small, as measured by the fall in density due to increased tem- perature. In the upper 5 m. are found from 43 to 50 per cent of the work and in this stratum the largest deductions from the apparent work are to be made for the influence of direct insolation. TABLE 6.—DISTRIBUTED WoRK, MEAN. - [NotE.—This shows work done in each stratum in distributing the heat brought to it, and in carrying on to the next stratum the heat which passes through it. This is computed only for the means of the lakes.) Canandaigua Lake. Cayuga Lake. Seneca Lake. Depth in meters. G.cm. |Percent.| G.cm. | Per cent.} G.cm. | Per cent. I, I00. § 45-0] 1,245.0 43+ 4 8. I 28.5 826.9 28.8 367-3 15.1 457-0 15-9 136.6 5:6 185.8 6.5 97-1 4o0 116. 5 41 28.3 I-2 29-5 Lo 10.4 “4 91 3 42 +2 2.9 +I u8 et Ba Bi, | esivisiarsaeraere «(Oils svete teva wif |sinicreitnceg HB fecereeeneafeernneeeetfene eee enee 1399904 Wine vs vecceare Dp AASE SH ca c sadnwitar 2,874.4 |occececeee SUBTRACTION CURVES. Table 7 shows the data for the mean subtraction curves of the three lakes. (See Birge, 1916, p. 384.) It shows the number of calories which pass through the several levels of the lakes and the amount of work needed to distribute them through the water below these levels. Comparison of the data at the surface shows that 12 to 14 cal. of heat are distributed through the subjacent water by 1 g. cm. of work. At lower levels the temperature declines and the decrease in density falls off even more rapidly with the result that an increasingly large number of calories -is distributed by 1 g. cm. of work. At the depth of 10 m. the ratio is 25 to 30 cal. to 1 g. cm.; at 20 m. the ratio rises to 40:1 or 50:1; at 30 m. in Seneca Lake and at 4o m. in the others it has risen nearly or quite to 100:1. This relation explains how in lakes of great depth a large quantity of heat is carried in spring to the lower water. The great quantity of work 222 BULLETIN OF THE BUREAU OF FISHERIES. needed for distribution in the upper water as the temperature rises equally makes clear the reason why the lower water soon ceases to gain heat as the season advances. In Seneca Lake work amounting to only 0.4 g. cm. is needed to distribute 512 cal. to depths below 70 m., while no appreciable amount of work is needed to distribute 347 cal. through the water below80m. The last statement is obviously not strictly accurate, but it is not worth while to compute the work in those cases where the decrease in den- sity due to increase of temperature is less than one part per million. TABLE 7.—SUBTRACTION CURVE MEANS: AMOUNT AND PER Cent or Heat in SuMMER Heat INCOME AND oF WorK NECESSARY TO DISTRIBUTE THIS Heat FOUND AT THE SURFACE AND AT DIFFERENT DEPTHS OF THE SEVERAL LAKES. [Nore.—Stated in units per square centimeter of the surface of the lakes.] Canandaigua Lake. Cayuga Lake. Seneca Lake. Depth in meters. - 7 Cal. P.ct. |G.cm.| P. ct. Cal. P.ct. |G.cm.| P. ct. Cal. P. ct. |G.cm.], P. ct. 29, 480 100.0 2,446 34,020 100.0 | 2,874 100.0 21, 860 74-3 | 15345 26,220 77.2 | 1,629 56.8 15,480 52-5 647 19,120 56-3 802 28.0 9,980 33-8 280 12,610 |’. 37-1 345 |. 120 6, 380 21.6 143 8, 160 24-0 159 5-6 3,280 Ir 46 3,960 _1Ie7 - 43 Ie§ 1, 880 4 18 2, 260 6.7 13 “5 1,110 3-8 8 I, 320 3-9 +2 700 2-4 4 900 2-6 “«O 440 15 2 630 Ie 280 1.0 ° 45° I. go a5 leases as ahs. 190 . HEAT AND WORK AS MEASURED AT DEPTH. In Table 7 the data are given in terms of the surface of the lake—so many calories, or gram centimeters, per square centimeter of surface. If the datum plane is taken as the area of the lake at the depth in question, the number of calories and gram centimeters at each level will be increased proportionally to the decrease of area as compared with that of the surface; but the ratio between the amounts of work and of heat would remain unaltered. ‘This relation is shown in Table 8. Perhaps the most interesting fact shown by it is the very close agreement between Cayuga and Seneca Lakes in both heat and work after the surface level is passed. Approximately equal quantities of heat pass through the 5 to 4o m. levels of both lakes. Cayuga Lake shows at the surface considerably less heat per unit of area than Seneca has, but this is largely due to the great area of shallow water at the north end of Cayuga Lake. No such area is found anywhere in Seneca Lake. The area of Cayuga Lake at 5 m. is about 79 per cent of the surface area, while that of Seneca Lake at the same depth is 87 per cent of the surface. The area of the 10 m. level in Cayuga is about 92 per cent of that at 5 m., and in Seneca about 93 per cent of the 5 m. level, a very close correspondence, which shows itself in the heat and work. The large area of shallow water in Cayuga Lake adds nothing to its effective area in absorbing heat, nor does it seem to diminish the efficiency of the lake. Canandaigua Lake, however, is plainly less efficient than either of the others. Its smaller area and higher banks cause this condition, since both factors lessen the efficiency of the wind. (See Birge and Juday, 1914, Pls. CXIII, CXIV, CXVI.) FINGER LAKES OF NEW YORK. 223 TaBLE 8.—AmoUNT oF Heat In SUMMER Heat INcoME AND WorK NECESSARY TO DISTRIBUTE I’. {Nore.—Expressed in units per square centimeter of the depth in question; not (as in other tables) in units per square centimeter of the lake surface.) Canandaigua Lake. Cayuga Lake. Seneca Lake. Depth in meters. Cal. G. cm. Cal. G. cm. Cal. G. em. OeSreis as 34 SERNA be Te Aare as eae See mtg Gak eed 26, 980 1,929 29, 480 2,446 34) 020 se ecik a ad Ai ARES SAR are Bi Phe a dc RTCA aes tial can ituatita a ce enny ae Znee 22,970 I,15o0 27,5750 1,710 28, 000 EO ssivics is: ste’ Soe el esatareteagete tbe wie a: loqmaeaclal atcliohinenetes Ve Gay Ge ns el ocalevabvagsnegsbayees Stasi guei del 16, 540 549 21, 440 892 21,900 F 4) 530 406 14900 9, 800 220 10, 100 51420 76 5,190 31440 33 3,150 2,330 17 1,980 1,640 9 1,480 1,150 5 I, IIo “B20 fives ci waves 840 |.. 2 420 |.. ieee aga 2 2 170 |.. ‘ go }.. silos Re AGS Re He een wea ° ABSORPTION OF SUN’S ENERGY. Observations were made in 1918 on Seneca, Cayuga, and Canandaigua Lakes in order to ascertain the rate at which the energy of the sun’s rays is absorbed by the water of the lakes. The instrument is described in another paper (Birge, 1921), and the description will not be repeated. It consists of a receiver containing 20 small thermal couples which can be lowered into the lake to any desired depth and alternately exposed to the sun and covered. The electrical effect of the sun’s radiation on the ther- mal couples is proportional to the energy in its rays, and the resulting electrical cur- rents are measured by the deflections caused in a d’Arsonval galvanometer. The galvanometer is kept on shore and is connected with the receiver by an insulated cable 100 m. long. : The observations on the three lakes afford excellent illustrations of the results obtainable by this instrument, and also of the difficulties which necessarily attend observations of the kind if made in the course of a short visit, when every opportunity must be fully used. The general results from each lake are clear and unmistakable, but in each case the details are affected by special conditions of sky or water. A part of the observations on Seneca Lake is given in Table 9 in order to show the nature of the data. 224 BULLETIN OF THE BUREAU OF FISHERIES. TABLE 9.—TRANSMISSION OF SUN’S ENERGY BY THE WaTER OF SENECA LAKE OrF HECTOR PoINntT, . Y¥., Auac. 1, 1918. [NorE.—1.so to 2.23 p. m., Government time=12.40 to 1.11 sun time, ‘Transparency 6.8 m.] Depth Depth Hour, p. m. PN Zero. soe ae Hour, p. m. nook | Zero. cog oe meters. meters. on ioe roe FENG ROPe accuse aearemnveanaten aceetye 400 ee ae 17-5 25 me ie 9053) || BO9eskey os ce asueee ees Sines 500 oe 7 one 11-9 50 a is Gare: |[OS ai acicuiccce na. peutsidgernbeavayeliss aie 600 ia aoe 8.3 100 te a8 90% ll BER wins ss parhepnradecsesaeas oo ees a 5:9 150 ine ae } rg Sie: | ae coda cave screened oe sieers 800 aes oe 4.0 200 ao pone BSF 2.28 catia se siotesewbinwtay salwene 900 a oF 2.9 sof 2] 4e8[h as ea ae 300 ee ae 24-2 |i o 28s ancien d KeteMedies 445 aera 1,000 aa ‘ te 2.2 sf ier] serif 2° . Bala NOTES ON ABOVE TABLE. a. Sky perfectly clear and sun’s radiation steady; no clouds; practically no haze. Light south air, causing ripples on surface. Some swell from wind of yesterday and of early morning. The swell caused irregularities of reading in upper water, as it raised and lowered the boat. At 100 cm. the scale moved over 4 to 5 divisions, and reading had to be estimated under these conditions. This effect became less as depth increased. Ripples cause a quivering of the reading i in the gelvationieter but are too small to cause swings of the scale. 2. In reading the direct sun a shunt coil is included in the circuit in order to keep the reading within the limits of the scale. This coil is cut out by a switch when the receiver is used in water. The reading in air must be multiplied by 1.89 to reduce it to the same scale as those in the water. Its value, therefore, on this occasion is 221 divisions. One division equals o.os9 cal./cm.?/min., so that the sun was delivering about 1.30 cal./cm.?/min. 3. The observations not reported included a repetition of several of the readings, anda second reading in the air, which gave a value of 116.2 divisions, or substantially the same as the first reading. 4. The numbers in the columns headed zero, reading, deflection, indicate divisions of the scale of the galvanometer. From these readings may be computed the value of the energy delivered by the sun at different depths of the lake, as is shown in the following table: TABLE 10.—CALORIES PER SQUARE CENTIMETER PER MINUTE FoUND at VARIOUS DEPTHS OF SENECA LAKE, AUG. 1, 1918. Depth in centi- Cal./em.2/|| Depth in centi- : Cal. /cm.?/ Depth in centi- Cal./cm.? meters. Percent. | “min. meters. Percent. | “nin. meters. pe ene an : 100. 0 1.30 12.8 O17 2,27. 0.035 31.8 +4 10.9 +14 18 + 023 29.0 ~38 9.0 12 3 +OL7 ai. 4. 28 9.7 10 Lo . 013 174 +23 5.4 07 15.0 -20 3.8 +05 FINGER LAKES OF NEW YORK. 225 TABLE 11.—TRANSMISSION OF SUN’S ENERGY PER METER OF DEPTH. (Nore.—Per cent of the energy found at the upper surface of each 1 m. stratum which is present at the lower surface of such stratum.] Trans- Trans- Trans- Stratum in meters. mission, Stratum in meters. mission, Stratum in meters. mission, per cent. per cent. per cent, OD sie ncait dee aio’ 83 She atroaunns. eee 214 69:6: |] BHGiss sectsisesconss waver 72.2 70. 2 69:8 fl OEtOis sme accixia tan eikonal 75:9 72.6 91.1 71.0 67.8 Table 11 is given as it stands in order to bring out the various small variations in percentage which are inherent in the observations. In all cases the fraction of a division of the galvanometer scale must be estimated and is, therefore, subject to error. The value taken as zero is not a fixed one and in any observation may be recorded slightly too low, or more probably a little too high. The motion of the boat, due to the swell, as stated above, might introduce some errors in this case, especially in the readings from the upper water. In figure 2 the results are plotted and a smooth curve a-a is drawn through them. All of the observations are very close to the curve. It is plain that there was transmitted through each 1 m. stratum of water below the surface meter about 71 per cent of the energy received at its upper surface. It is not probable that the higher transmission indicated in the 9 to 10 m. stratum has any significance. A reading of 2.1 divisions of the scale at 10 m. instead of 2.2 divisions would bring this interval into line with the others. Lake water differs widely from pure water in the quantity of energy transmitted. If we assume a solar energy curve corresponding to a path of the rays in the air of 1.5 atmosphere, with about 0.5 cm. condensable water in the atmosphere, about 47 per cent of the solar energy will be left after passing through 1 m. of pure water. The water of Seneca Lake, therefore, cuts off about 25 per cent more than does pure water and adds one-half to the loss due to pure water. Pure water transmits through the 1 to 2 m. stratum nearly 80 per cent of the energy reaching its upper Jevel and over go per cent passes through all deeper 1 m. strata, the loss per meter rapidly declining to a minimum of about 2 per cent of the energy incident on the upper surface of the stratum. At 5 m., therefore, there would remain about 29 per cent of the original energy of the sun and about 23.4 per cent at 10 m. instead of 5.4 per cent and 1 per cent found in Seneca Lake. This wide difference between pure water and the lake water is probably due chiefly to matter suspended in the water of Seneca Lake, since there is very little stain present in the water. The suspended matter is partly organic but chiefly fine silt derived from the soft shales that constitute much of the shores. In pure water the transmission through the 1 to 2 m. stratum is much smaller than in those below. This is due to the rapid absorption of the rays of the red end of the ‘spectrum as compared with the slow absorption of the shorter waves. No such effect uiseems to be present in the Jake, nor is it ordinarily demonstrable in lakes. Sometimes, but not commonly, the deeper strata of a lake show a transmission 1 or 2 per cent higher than the 1 to 2 m. stratum, but in general the transmission in that stratum is nearly the same as in those immediately below. This means that the large nonselective ab- 46104°—21——-3 226 BULLETIN OF THE BUREAU OF FISHERIES. sorption due to turbidity and the selective absorption due to stain obscure the selective absorption of the water, as water, after the first meter has been passed. In that meter of water is absorbed practically all of the energy contained in that part of the spectrum Per cent 6 10 16 20 26 30 / Tt / i | oi Fag. 2.—Curves of transmission of sun’s radiation, Seneca Lake, Aug. 1, 1918. ‘The vertical axis gives depth and the horizontal axis gives per cent of the total radiation of thesun. A-A, direct observations; B-B, verticalsun; C-C,mean sun. Thesun’s rays passed through a thickness of 100 cm. water of the lake at the depth of94em. Dotsare placed corresponding to this depth on the curve A-A, and from these is plotted the curve B-B, for thesun in the zenith when depth and stratum traversed by rays are equal. ‘The rays pass through a mean distance of 115 cm. during the warming season in reaching a depth of 100 cm. These points are marked on the curve B-B, and from them is plotted the curve C-C or the curve of meansun. (See Table 12, Pp. 228.) lying below the A line which is commonly taken as the lower limit of the visible spec- trum. The general result of these observations is, therefore, plain. Under the conditions of the time and place 21 to 22 per cent of the sun’s energy delivered to the surface was FINGER LAKES OF NEW YORK. 227 present at a depth of 1m. In the deeper 1 m. strata there was a loss of 28 to 29 per cent of the energy present at the upper surface of the stratum. At 5 m. depth there remained about 5.4 per cent, and at 10 m. about 1 per cent of the energy delivered to the surface. We may infer from such a set of observations the penetration of the sun’s rays during the whole day or during a longer period, assuming that the turbidity and color of the water remain unchanged. In such a process it is not hard to secure results which are correct in general, but it is impossible to secure minute accuracy. Certain, though not all, of the facts which prevent minute accuracy will be mentioned. 1. Sunlight is a mixture of the direct rays of the sun and of rays reflected from the sky. The percentage of sky radiation is very variable, being sometimes as low as 8 per cent of the total radiation and rising nearly to 100 per cent when the sun barely shines through haze or cloud. The quantity of energy reflected from a unit area of sky is also variable and differs with the nature of the sky and the proximity of the area to the sun. The mean percentage of sky radiation reflected from the surface of the water differs from that of the direct rays, and the mean path in water of the rays from the sky differs from that of the direct rays. It is practically impossible, under the conditions of ob- servations on lakes, to determine either the amount or the distribution of the sky radia- tion. It is, therefore, impossible to make full correction for the elements in the mixture of direct and diffuse rays at the time of observations. 2. It is also impossible to make such corrections for longer periods, since the aver- age amount of sky radiation is still quite unknown for most places, and is not accurately known anywhere. 3. No correction has been made in the observations for radiation reflected from the surface of the water, but the readings at 1 m., etc., have been compared directly with the reading in air. The direct sun radiation, at the altitude of the sun when the observa- tions were made, would lose about 2.1 per cent by reflection. The sky radiation would lose 17.3 per cent if equal quantities came from equal areas of sky. ‘This loss at the surface, which can not be known accurately, has been balanced against the opposite effect of the hemispherical glass cover of the sunshine receiver. There would be about 4 per cent of the sun’s radiation reflected from this in air and about 0.5 per cent in water. In computing a standard curve of absorption for Seneca Lake, all radiation has been referred directly to the sun, and the path of the rays in the water has been computed on that basis, from the following elements: Time of observations, August 1, 1918, 12.40 to 1.11 sun time. Corresponding altitude of sun, August 1, 64.1 to 62.3°- Depth at which sun’s rays pass through 1 m. of water, at first observation, 94.5 cm; at last observa- tion, 93.7 cm.; mean 94.1 cm. On the curve of direct observations (A—A, fig. 2) are noted the readings at the dis- tances corresponding to this path of the rays in water. These periods are plotted and connected by a new curve, B-B, the curve for vertical sun. In this curve, which assumes a sun in the zenith, the depth below the surface equals the length of path of the rays in reaching that depth. This constitutes a standard curve, from which may be derived the energy which remains at given depths below the surface at any time of the day or year, provided the altitude of the sun is known and the corresponding length of the path of its rays in water. It must be assumed also that all radiation comes directly 228 BULLETIN OF THE BUREAU OF FISHERIES. from the sun, or at least that the value of the sky radiation is the same as at the time of observation. The results are stated in Table 12, vertical sun. The mean distribution of sunshine and cloud at Seneca Lake is not known, but at Madison, Wis., the mean daily supply from sun and sky during the five months April 1 to August 31 is 398 cal. The mean path of the rays during this period to reach a depth of 100 cm. below the surface is 115 cm. In this computation allowance is made for reflection from the surface in excess of 2.1 per cent; all radiation is supposed to come from the sun; and the form—though not the area—of the solar energy curve is supposed to be constant. The points corresponding to this distance of 115 cm. per 100 cm. of depth are noted on the curve for vertical sun, carried up to their proper place, and a third curve, C—C, figure 2, is drawn, which is the curve for mean sun (Table 12). TABLE 12.—TRANSMISSION OF SuN’S Rays BY WATER OF SENECA LAKE, AUG. 1, 1918. (See fig. 2, p. 226.) Per cent radiation remaining Per cent radiation remaining at depth indicated. at depth indicated. Depth in centimeters. Computed per cent. Depth in centimeters. Computed per cent. Observed Observed per cent. | Vertical Mean percent. | Vertical | Mean sun, sun, sun. sun. 21.4 21.9 20. 7 3.8 44 3-3 15.0 15.6 14.3 ae 3.2 2.3 10.9 Il. § 9.9 18 2.3 1.6 27 8.3 6.8 zig) 7 1.0 5.4 6.0 47 Lo Ee a7. This curve of mean sun and Table 12 show that in Seneca Lake at 1 m. depth there is found an average of about 20.7 per cent of the incident radiation and that each 1 m. stratum below transmits less than 70 per cent of the radiation received by its upper surface. The water has absorbed 99 per cent of the incident energy at about 9 m. as compared with about 10 m. for the observed curve and 11 m. or more for the curve of vertical sun. The difference in the three curves are not striking in this case; but if the observa- tions had been made at an hour farther from noon, or later in the season, the difference would have been correspondingly larger. It must not be supposed that this mean sun curve represents exactly the mean con- ditions actually present during the period when the lake is warming. ‘The transparency of the water is variable and the sun’s penetration varies with it. No account is taken in this curve of the energy received during cloudy hours. Yet after all deductions are made it remains true that the curve gives a generally correct picture of the actual direct delivery of the sun’s radiation to Seneca Lake so far as a single observation can give this. Hardly more than 20 per cent of the incident energy is delivered to water below the surface meter. Not over 5 per cent is delivered to a greater depth than 5 m. and not over 1 per cent below 10m. Evena considerable increase in transparency would leave these figures, not unchanged, but of the same order of magnitude. Observations such as these are ordinarily made at times when the sky radiation is relatively small—near noon of clear days. When, therefore, such an observation is FINGER LAKES OF NEW YORK. 229 used as the basis of larger conclusions and when in computing the results all radiation is assumed to be direct, the effect of the direct rays of the stm in warming the lake is placed at a maximum. In the preceding paragraph all radiation is supposed to come directly from the sun. In fact at Madison about 16 per cent of the total radiation Oo __G.em. 60 100 180 200 250 B_ 00 ed — — n. — ZK o 10 Lt 1B i” 35. FEC Fic. 3.—Work curves of Seneca Lake, mean temperature. The vertical axis shows depth; the horizontal axis shows gram centi- meters of work per meter of depth and square centimeters of surface of lake. OCC, curve of direct work. About rq5 g. cm. of work, for instance, are necessary to carry the heat of the 9 to 10 m. stratum from the surface and put it in place. BDE, curve of distributed work, derived from OCC, showing the amount of work done in each 1 m. stratum. The area OBEFO (distributed work) is equal to the area OCCFO (direct work). ODD shows the contribution of the sun in distributing the sun’s energy. The area ODDBO gives the contribution of the sun, and that of the wind is represented by the area ODEFO. (See Table 16, p. 235.) 5 received April 1 to August 31 comes during cloudy hours, and about 16 per cent more comes from the sky during sunny hours. The direct sun, therefore, supplies only about two-thirds of the radiant energy received by the lake. It may be assumed that during cloudy. hours equal areas of sky supply equal amounts of energy to a surface normal to the rays. On this basis, and allowing for reflection from water surface, the mean path of 230 BULLETIN OF THE BUREAU OF FISHERIES. the diffuse radiation in reaching a depth of 100 cm. would be about 126 cm. as compared with 115 cm. for the direct rays. The mean path for sky radiation during sunny hours would be between the numbers given above, depending on the relative amount of the sky radiation coming from areas close to the sun and, therefore, having approximately the same length of path in the water as the sun’s rays have. In the absence of knowledge of the amount of sky radiation at Seneca Lake, either general or on the date of observation, no correction can be made for sky radiation. Such correction can be made where observations are so numerous that it may safely be assumed that sky radiation was the mean amount. ‘This is the case with Lake Mendota, and the best computation that can be made shows that the mean path of all rays to reach a depth of 100 cm. in the period of April 15 to August 15 is about 118 cm. No essential difference, therefore, is made in the results if all radiation is attributed to the sun with a mean path of 115 cm., as has been done in the previous paragraphs. The observations on Canandaigua and Cayuga Lakes may be treated much more briefly. They were taken at the same intervals as on Seneca Lake but to the depth of 5 m., which is ample for the determination of the rate of absorption. The results are shown in figures 4 and 5, and summarized in Tables 13 and 14. TABLE 1 3.—TRANSMISSION or RapiaTION BY WATER oF CayuGa LAKE, SHELDRAKE Porn’, Juuy 29, 1918, 1.45 TO 2.45 P. M., GOVERNMENT TIME. (See fig. 4.) {Nove.—Sky with cumulus clouds drifting across; clear between clotids. Transparency of water 6.2m. ‘Transmission per meter about 66 per cent.) Per cent radiation remaining at depth Per cent radiation remaining at depth indicated. indicated, Depth in centi- Computed per cent. Depth in centi- Computed per cent. meters. Mean meters: M Mean ae ébserved : ee observed per eent.| Vertical Mean pe ‘| per cent. | Vertical| Mean sun. sun. sun. sun. | Ig.2 I9- 4 19-9 17-9 : 6 pC 19-6 i GOO eee cece ee eeee { ou } 55 6.1 49 13-4 : 3-6 BOO Mrechieayenslatak 36 85 II-3 12.8 13-3 11.9 Hl 34 II-4 | BOOK 4:dsincisnntagsns va 36 3-6 Ael 3-1 8.1 8.4 9-1 7.6 : 8 4 BOG ve eitdcisreimainaies Be 8.6 = 2 i Oo Gen. 80. 100 150 200 20 B a00 poe ce one me = nm. Wilt ~ Lo Fic. 4.—Work curves for Cayuga Lake. (See explanation, fig. 3.) The observations on Cayuga Lake are rendered somewhat irregular by the fact that numerous white cumulus clouds were passing over the sky and work had to be done when the sun was in the spaces between the clouds. Under these conditions the FINGER LAKES OF NEW YORK. 231 radiation from the sun is sure to be variable; the approach to the sun of a white cloud momentarily raises the radiation and unnoticed wisps of cloud may reduce it. In the series it is clear that the mean of the readings at 200 cm. is too low as compared with all of the others, since.the transmission in the 1 to 2 m. stratum should be about the same as below. The value of 12.8 per cent has been assumed, therefore, for the 200 cm. level and a mean transmission of about 66 per cent per meter. Under these condi- tions about 99 per cent of the sum’s energy would be delivered to the upper 8 m. of water, somewhat more than 80 per cent going to the first meter, or with mean sun about 82 per cent. It will be noted that corresponding with the smaller transparency of the water, as compared with Seneca Lake, the transmission of radiation is decidedly lower. TABLE 14.—TRANSMISSION oF SuN’s ENERGY BY WATER OF CANANDAIGUA LAKE, JULY 27, 1918, 11.37 A. M. TO 12.03 P. M., GOVERNMENT TimME. (See fig. 5.) [Nore.—Sky hazy. Transparency of water 4.4m. Transmission pet meter about 60 per cent.) | Per cent radiation remaining Per cent radiation Ttemaining at depth indicated. at depth indicated. * =~ = Depth m cetitimeters. Computed per cent. ||. Denth in centimeters. Computed per cent. Observed Observed percent. | Vertical | Mean per cent. | Vertical | Mean sun, sun, sun. sun, BOG oo senna csiaidvortaye ded odsormateruie ain 18.7 19.4 OH dO setecd dine Man aRaWaemiine Hine 4.2 4.8 3.7 BOO) x5! ipacdausyinacavayess are Lee peac adnate 11.3 12.2 LO! || SOO: ccrcawesiwe tia aouwaiiicns as 3.1 Sat 2.2 BOO nS id eta heeend sceaeieciy a 6.9 7.8 6.3 O_G.cm. 80 100 180 200 B_ aso ‘a =r ee ou Cm, ~J NN } D A ‘ LL 4, ZA e 20 sna Fic. 5.—Work curves for Canandaigua Lake. (See explanation, fig. 3.) The observations on Canandaigua Lake were also somewhat irregular, not on account of clouds, but haze. The sky was cloudless, but the hills a few miles up the lake were nearly invisible in the haze which filled the valley. Under such conditions the value of the sun’s radiation is much reduced, and it was found to be about 0.95 cal./cm2/min. as compared with 1.30 cal. in the case of the two other lakes. The read- ings of the sun at the beginning and end of the observations in the lake were in close agreement. The readings of the first series taken in the water—those taken while the receiver was going down—were also in close agreement and indicate that 18 to 19 per cent of the radiation in air was present at 100 cm. depth and that each meter below that depth transmitted about 60 per cent of the radiation received by its upper 232 BULLETIN OF THE BUREAU OF FISHERIES. surface. At 500 cm., however, the reading rose so that the transmission seemed to rise to about 74 per cent. The second set of readings—those taken while the receiver was being raised—again indicated about 60 per cent transmission but showed at all depths a higher percentage of the radiation at the surface, amounting at 100 cm. to 21 per cent. Comparison with the other lakes shows that the lower value at 100 cm. is to be chosen, as the transparency of the water is decidedly less than in either Cayuga or Seneca Lakes. ‘The haze must have become slightly thinner during the later readings in the water but thickened again before the second reading in the air. The accuracy of the value at 100 cm. must remain somewhat uncertain under the conditions of sky then prevailing. Since the value of the radiation may alter during haze almost from minute to minute with no visible indication of change, such as cloud offers, it would need a very large number of readings to show whether 18 to 19 per cent or a slightly lower figure should be taken as the value for mean sun at 100 cm. The error is not likely to exceed 1 per cent in any case, nor is it large enough to affect general relations of sun to the distribution of heat. Under these conditions 99 per cent of the sun’s energy would be delivered to the upper 6.5 m. of water. We may now put togetlier the general results from the three lakes in which observa- tions were made. TABLE 15.—TRANSPARENCY AND TRANSMISSION OF RADIATION—VERTICAL SUN. Trans- | Per cent fen cae parency at 100 dniesicu in centi- meters. | meters. adeter Seneca Lake 21.9 72 Cayuga Lake... ... 6.2 19.9 66 Canandaigua Lake. 44 19. 4 60 In these cases there is some parallelism between the percentage of transmission and the transparency of the lake. This is due to the fact that all these lakes have water which is only slightly stained and which does not differ greatly in color. In general there may be little correlation between transparency and rate of transmission. WORK OF THE SUN IN DISTRIBUTING HEAT. From the data at hand it is possible to make a general estimate of the part which the sun plays in distributing the heat gained by Seneca Lake as its summer heat income. We have as data (a) the amount of heat so gained as the mean of four seasons; (b) the amount and the distribution of the work necessary to carry this heat through the lake, assuming that all work is done by the wind; (c) the actual amount of heat delivered into the water of the lake directly by the sun on one date, and the conclusions drawn from these observations in the preceding paragraphs. We lack as data (a) the total amount of heat delivered to the lake during the period when the summer heat income is gained; (b) the losses of heat during this period from different strata near the surface. The absence of the data specified and others as well make it impossible to state the réle of the sun with any approach to exactness. But it is possible to make esti- FINGER LAKES OF NEW YORK. 233 mates which will show the general situation and in our almost complete ignorance of the subject, such statements are not without value. We take, therefore, as the summer heat income of Seneca Lake 34,000 cal./em.? of surface. Of this sum, 32,400 cal. are found below 1 m.; 28,000 cal. below 5 m.; and 21,900 cal. below 10 m. These figures are based on the calories found per square centimeter of the depth in question, and not those per square centimeter of the surface. In computing the relative work of sun and wind these figures must be used, since the sun’s radiation which passes through the shallow water is absorbed by the bottom of the lake. The distribution of this heat, attributing all work to the wind, requires about 2,874 g. cm. of work per square centimeter of the lake’s surface. This work is distrib- uted (fig. 3) at the rate of about 290 g. em./cm.? of the surface at the surface; 270 g. cm./cm.? at 1 m. depth; 202 g. cm./em.? at 5 m.; and 125 g.cm./em.2 at 1om. In the upper 5 m. there is done about 45 per cent of the total work; about 33 per cent in the 5 to 10 m. stratum, both of which are within reach of the direct influence of the sun; about 20 per cent more of the work comes in the 10 to 15 m. stratum. Applying the experience gained from observations on Lake Mendota, it may fairly be assumed that Seneca Lake receives about 65,000 cal./cm.? of surface during the period of the summer heat income. ‘The lake loses, therefore, about one-half of the incident heat. If we apply the mean sun data of Table 12 to this gross income, the sun delivers during this period about 13,400 cal. to the depth of 1 m.; 3,000 to 5 m.; and 450 to 10m. ‘These numbers are, respectively, 41 per cent, 11 per cent, and 1.9 per cent of the quantity of heat which passes through these levels. (See Table 7 for quantity of heat.) The work attributed to the wind at these depths would be diminished by the aid of the sun in the same ratio that the heat delivered by the sun bears to the total amount of heat passing through those levels. Computed on this basis, the sun does all of the work of distributing heat at the surface, 41 per cent at 1 m. depth, 11 per cent at 5 m., etc. These quantities may be plotted as on figure 3 (p. 229) and the points connected by acurve. Then the area ODBO is proportional to the total work done by the sun under the conditions assumed. ‘This area may be measured with a planimeter. It is equal to about 16 per cent of the area representing the total work. The part of it below 1 m. is about 10.9 per cent of the work done below 1 m. of depth. This represents the maximum possible aid which, under the conditions assumed, the sun can give in the distribution of heat, for it assumes that the entire loss of inci- dent radiation by the lake, amounting to one-half of that received, falls on the wind- placed heat and that no loss falls on the sun-placed heat. This assumption is evidently not correct. If, instead, we assume that the sun-placed heat suffers equal losses with that distributed by the wind, the aid of the sun will be reduced to about 8 per cent of the total work done and to about 5.5 per cent of the work done below 1 m. Probably the assumption of equal losses is unfair to the sun. A great part of the lost heat is in that which is absorbed by the thin stratum at the surface and is used in evaporation, lost to the air at once or during the following night, etc. Almost all of the heat in the longer waves of the spectrum is absorbed by a much thinner layer of 234 BULLETIN OF THE BUREAU OF FISHERIES. water than 1 m. Schmidt (1908, p. 240) computes that about 27 per cent of the solar energy is absorbed by 1 cm. of pure water and about 45 per cent by 1 dm. He uses Langley’s energy curve for the solar spectrum, which makes his figures somewhat larger than would be the case in a curve for moderately high sun. In the curve which we have used as standard (path of rays equals 1.5 atmospheres) about 43 per cent of the energy would be absorbed by 25 cm. of pure water and 49 percent by 50cm. While no great accuracy can be claimed for the figures shown by Seneca Lake of about 67 per cent absorption for 25 cm. and 72 per cent for 50 cm., they are probably not greatly in error. The differences between them and the data for pure water are much the same as for greater depths. Thus more than one-half of the sun’s energy is delivered to the upper centimeters of water from which loss to the air is easy. But much of the heat so delivered is distributed by the wind from the surface strata to deeper water, especially in the early part of the warming season when the lake is gaining heat rapidly. From this source comes the greater part of the heat which the lake gains below 1 m. in excess of that delivered by the sun. This heat amounts to 19,000 cal./em.’ and much of it must come from the 40,000 cal./cm.?, or more, absorbed by the upper 25 cm. of the lake. During bright and windy days there must be thus moved down into the lake by the wind much héat which is lost during cool periods when the whole upper water of the lake cools down. It is true that on the whole the heat delivered by the sun to strata below the surface is more likely to be retained, as the water above a stratum must be cooled to a lower temperature than the deeper water before any heat can be lost by the latter. But several times each season there is a general cooling of the upper water, when much heat is lost, that placed by the sun as well as that placed by wind. At present, therefore, no accurate estimate can be made of the loss of sun-placed heat at various depths. The subject must be left here with the general statement that between 84 and 92 per cent of the work done in distributing heat through the water of Seneca Lake is performed by the wind, on the assumption that conditions of trans- parency, etc., on August 1 were average ones. The amount really attributable to the sun is probably as much as 10 to 12 per cent. More than this can not be said, both in view of considerations presented above, and also in view of one other consideration which the study of Lake Mendota has shown. In the early part of the warming period, when gains of heat are rapid and when the deeper water is securing most of its heat, the sun plays a small part in distributing the heat. Later in the summer the sun has a much larger share of the work, when the epilimnion is forming, when gains of heat are small (perhaps only 5 to 10 per cent of the incident radiation), and when these gains are confined to the surface strata. The foregoing paragraphs have dealt with Seneca Lake alone. ‘The same methods may be applied to the other lakes with similar results. It is unnecessary to give the details of the computations; the results are shown in Table 16 (p. 235) and figures 4 and 5 (pp. 230, 231). FINGER LAKES OF NEW YORK. 235 TaBLe 16.—DIvision or DistRiBut1on oF SUMMER Heat INCOME BETWEEN SUN AND WIND IN THE LAKES AS A WHOLE AND IN THEIR SEVERAL Strata. (See figs. 3, 4, 5, and text.) (Nore. —In this table, as elsewhere in this paper, ‘work’ means the total work which would be needed to distribute the heat from the surface of the lake through the adjacent water, computed on the assumption that all heat is put into place by the wind mixing the warmer surface water with the cooler water below. In the division of the task of distributing heat between sun and wind it is also assumed that all losses of heat fallon wind-placed heat. This evidently attributes too large a share » ripe ei ce a fair estimate would be to allow to the sun all that it does below 1 m., i. e., about 10 to 11 per cent ol e to’ Canandaigua Lake. Cayuga Lake. Seneca Lake. Sun. Wind. Sun, Wind. Sun. Wind. Per cent, | Per cent. | Per cent, | Per cent. | Per cent. | Per cent. Total work sighs sich seoetisostsihy aa as aaccanee ae da as eR leloe ys deg pamepete 16.9 83.1 15.0 85.0 15.8 84.2 Work, otosm... sa 31.6 68. 4 33-1 66.9 32.0 68.0 Work, 5 to 1om 2.9 97.1 4.6 95-4 6.6 93-4 Work, oto rm. 62.3 37-7 60. 8 39. 2 58.3 51.7 Work, below x m. 10. 5 89. 5 10.0 90. 0 Ilr 88.9 Work, below 5 m 7 98. 3 2.4 97.6 3 96. 7 Total work of sun and wind.............6..050006 cece eee 1,929 g. cm. 2,446 g. cm. 2,874 2. cm. PLANKTON. The fresh-water organisms which constitute what is known as the plankton may be separated into two groups, namely, (a) those forms which are large enough to be captured readily with a regular plankton net whose straining surface is made of bolting cloth, size No. 20 (new No. 25) and (6) those forms which are so small that they readily pass through the meshes of this bolting cloth. The former constitutes the net plankton and the latter may be called the nannoplankton. The latter term has been applied specifi- cally to those organisms whose maximum diameter does not exceed 25 4; but it is pro- posed to extend the meaning of this term to include all of the material that passes through the meshes of the net. The terms “macroplankton” and ‘‘microplankton’’ have been used to designate these two groups. METHODS. The net plankton was obtained by means of a closing net which has been fully described in a previous paper so that it is not necessary to consider it further here (Juday, 1916). ‘The coefficient of this net is 1.2; that is, about 80 per cent of the column of water through which it is drawn is strained. The catches from the different strata were concentrated in the plankton bucket; the material was then transferred to 8-dram vials and preserved in alcohol. In the enumeration the volume of the catch was reduced to ro cm.?; after shaking thoroughly 2 cm.® were removed with a piston pipette and the crustacea and rotifers contained therein were counted with a binocular microscope. The number thus obtained multiplied by the factor five represents the total of such organisms in the catch. When only a few of the larger crustacea were present, the total number was ascertained by direct count. The smaller organisms, such as the Protozoa and alge, were enumerated by placing 1 cm.’ of the material in a Sedgwick-Rafter cell and ascertaining the number of the various forms in the usual manner by means of a compound microscope. Samples of water for a study of the nannoplankton were obtained by means of a water bottle. ‘The minute organisms were secured from these samples by means of an electric centrifuge having a speed of 3,600 revolutions per minute when carrying two 236 BULLETIN OF THE BUREAU OF FISHERIES. 15 cm.° tubes of water. The sedimentation was usually completed in about six minutes. The material was then transferred to a counting cell with a long pipette and the organ- isms were enumerated with a compound microscope having a 16 mm. objective and a No. 8 ocular. Many of these organisms, more especially the minute flagellates, are de- stroyed by the various preserving agents, so that it is necessary to have the living material for these enumerations; such counts must be made, therefore, as soon as possible after the samples of water are obtained. The results obtained in the various enumerations are shown in Tables 17, 18, and 21. The figures indicate the number of individuals per cubic meter of water at the different depths. For purposes of comparison the results obtained for net plankton on Canandai- gua, Cayuga, and Seneca Lakes in 1910 are shown in Table 18. Observations were made on the net plankton and nannoplankton of Green Lake, Wis., in 1918, soon after these were made on the Finger Lakes, and these have been included in Tables 17 and 21 for comparative purposes also. NET PLANKTON. Phytoplankton.—Table 17 shows that the green and blue-green alge were scarce in the three Finger Lakes at the time of the observations in 1918. Only three forms were present, namely, Anabaena, Microcystis, and Staurastrum. In Canandaigua Lake a relatively small number of colonies of Microcystis was found in the upper 10 m. and Staurastrum was noted in the ro to 40 m. stratum. In Cayuga Lake Anabaena was obtained in the upper 5 m. and Microcystis in the upper 10m. In Seneca Lake this group was represented only by a few colonies of Microcystis in the 10 to 15 m. stratum. A comparison with Table 18 shows that fewer forms were present in 1918 than in 1910 and also that the number of individuals was much smaller in the former year. The two sets of catches on Canandaigua Lake present the most marked difference in this respect. The net catches from Green Lake, Wis., contained a much larger algal population than the Finger Lakes, owing to the presence of a large number of filaments of Oscil- latoria. This form was unusually well represented in the upper 15 m., a maximum of nearly two million filaments ver cubic meter of water being found in the o to 5 m. stratum. _- Inthe Finger Lakes the most abundant diatom, both in 1910 and 1918, was Aster- ionella, while Fragilaria was second in importance both years. In Canandaigua Lake the diatom population was substantially the same in these two years, while in Cayuga Lake the number was much larger in the former year. In Seneca Lake, on the other hand, the number was larger in 1918 than in 1910. In Green Lake Asterionella was the only diatom noted, a few individuals of this form being present in two catches. Zooplankton.—Uroglena was fairly abundant in the upper 30 m. of Canandaigua Lake and a few colonies of Epistylis were noted in the 5 to 10 m. stratum. In 1910 Ceratium was the most abundant protozoan in this lake; but it was not found in 1918. In Cayuga Lake Actinosphaerium and Ceratium were about equally numerous in 1918, both being most abundant in the upper 15m. ‘The former was not found in 1910. and the latter was much more abundant in this year than in 1918, the number reaching more than a million and a half per cubic meter in the 0 to 5 m. stratum. Dinobryon was not as abundant in 1918 as in 1910 and Mallomonas was not noted in the former year. FINGER LAKES OF NEW YORK. 237 In: Seneca Lake Ceratium and Dinobryon constituted the protozoan population. A relatively small number of the latter was noted in the 5 to ro m. stratum. Ceratium was distributed through the upper 20 m. but was most abundant in the upper 5 m. The rotifer population was largest in Cayuga Lake and smallest in Canandaigua Lake in 1918. In the latter lake rotifers were most numerous in the upper io m. while in Cayuga and Seneca Lakes the largest number was found in the upper 15 m. The maximum number of individuals in the rotifer group was noted for Synchaeta in Cayuga Lake, where it reached 44,700 per cubic meter of water in the 10 to 15 m. stratum; the average number in the upper 15 m. was 35,950 individuals. This form was not found in the other two lakes. Polyarthra was noted in the catches from each of the three lakes in 1918, but it was most numerous in Cayuga Lake, reaching a maximum of 21,000 individuals per cubic: meter in the 5 to 10 m. stratum. The maximum number in this lake in 1910 was a little more than ten times as large as this. Conochilus was also found in the catches from each of the three lakes, but it, too, was most abundant in Cayuga Lake, reaching a maximum of 33,750 per cubic meter in the o to 5 m. stratum. A few individuals of Anuraea cochlearis were found in the upper water of Canan- daigua and Seneca Lakes, but this form also was distinctly more numerous in Cayuga Lake. The catches from Canandaigua Lake contained a few specimens of Notholca longispina, and the material from Cayuga Lake showed the presence of a few individ- uals of Asplanchna and Ploesoma in the upper water. The rotifer population of Canandaigua Lake was substantially the same in 1918 as in 1910. (See Tables 17 and 18.) In Cayuga Lake Polyarthra was not nearly as abundant in 1918 as in 1910, but the other forms were more numerous, in general, in the former year. In Seneca Lake not so many forms were represented in 1918 as in 1910, but those that were present were more numerous, so that the total rotifer popu- lation was somewhat greatef in the former year. In Green Lake the rotifers were more abundant than in Canandaigua Lake, but they were not as numerous as in Cayuga Lake; the number in the upper 20 m. was substantially the same as that of this stratum in Seneca Lake. Copepod nauplii were most abundant in the upper 20 m. or 30 m. of each Jake, but they were present in the lower strata also. A larger number was found in Seneca Lake than in the other two lakes and the number in Seneca Lake was larger in 1918 than in 1910. In the other two lakes they were more numerous in the latter than in the former year. ‘They were more abundant in Green Lake than in any of the Finger Lakes. Three genera of copepods were represented in the net catches from each of the three Finger Lakes, namely, Cyclops, Diaptomus, and Limnocalanus; while a fourth, Epischura, appeared in the 5 to 10 m. stratum of Canandaigua Lake. By far the greater portion of the copepod population consisted of Cyclops and Diaptomus, the former being numerically greater than the latter in each of the lakes. Both of these forms were more abundant in Seneca Lake than in either of the other Finger Lakes. In the former the maximum number of Cyclops was 25,100 per cubic meter in the o to 5 m. stratum, with an average number of 21,460 in the upper 15 m. The maximum number of Diaptomus was 9,810 per cubic meter in the 15 to 20 m. stratum of Seneca Lake. Limnocalanus was present in the catches from each of the three Finger Lakes, but was confined to the deeper water. 238 BULLETIN OF THE BUREAU OF FISHERIES. In Canandaigua Lake the Copepoda were more numerous in 1910 than in 1918, but the reverse was true of the other two lakes. ; The number of Diaptomus was larger in the upper strata of Green Lake than in any of the Finger Lakes, but Cyclops reached a larger number than in Seneca Lake only in the o to 5 m. stratum. The Cladocera consisted of representatives of Sida, Diaphanosoma, Daphnia, Ceriodaphnia, and Bosmina. Bosmina was the most abundant form, and it was present in the water of Cayuga and Seneca Lakes in much larger numbers than in Canandaigua Lake. The maximum number obtained was 19,100 per cubic meter of water in the 10 to 15 m. stratum of Seneca Lake. The average number in the upper 15 m. of Cayuga and Seneca Lakes was 12,770 and 11,200 individuals per cubic meter, respectively. ' Ceriodaphnia was found only in the 5 to 10 m. stratum of Cayuga Lake and Sida only in the o to 5 m. stratum of this lake. Diaphanosoma was noted only in the o to 5 m. stratum of Canandaigua Lake. Daphnia retrocurva was obtained from the upper 30 m. of Canandaigua Lake, and a few young of this species were present in the 5 to 15 m. stratum of Cayuga Lake and in the 10 to 15 m. stratum of Seneca Lake. In Canandaigua and Cayuga Lakes Cladocera were more abundant in 1910 than in 1918, while the reverse was true of Seneca Lake. The Cladocera were more numerous in Green Lake than in Canandaigua Lake, but they did not reach as large a number as in Cayuga and Seneca Lakes. The numerical data serve to give a reasonably accurate notion of the plankton popu- lation of these lakes, but such data alone do not give an adequate idea of the relative value of the various forms as a source of food for other organisms. When they are combined with data relating to the weights of the different organisms their value is very greatly enhanced. By means of small platinum crucibles and a sensitive assayer’s balance the weights of the more important crustacean constituents of the plankton were obtained and the results of such determinations are shown in Table 19. Such data have also been secured for various constituents of the plankton of Wisconsin lakes and where such results were not obtained for some of the forms from the Finger Lakes, those from the former lakes have been used in computing the data shown in Table 20. The dry weight was obtained for all of the material and the wet weight as well for a few of the forms; after taking the dry weight the material was ignited in an electric furnace for the purpose of ascertaining the percentages of organic and inorganic matter. In computing the data for crustacea in Table 20 the number of crustacea per cubic meter of water in astratum was multiplied by the volume of that stratum and the total for the lake was ascertained by adding the numbers in the various strata. This total multiplied by the weight of the particular organism under consideration gave the amount of such material in the entire lake; this quantity divided by the surface area of the lake gave the weight per unit area, which is expressed in the table in kilograms and pounds per square kilometer and acre, respectively. The amount of material per unit of surface is larger in the deep water than in the shallow water, but the sides of these lakes have such steep slopes that the results would not be altered very materially by taking this fact into consideration. Also it must be borne in mind that these figures are based upon a single set of catches in each lake FINGER LAKES OF NEW YORK. 239 and that a more extended series of observations might have yielded somewhat different results. The data in hand, however, are sufficient for a fairly good estimate. No organisms were weighed in 1910, but for purposes of comparison the data obtained in 1918 have been applied to the numerical results of the former year. In 1910 Canandaigua Lake possessed the largest amount of crustacean material, having about 2,579 kg./kim.? of surface, while Seneca Lake was second with slightly more than three-quarters of this amount. Cayuga Lake, however, was less than 10 per cent below Seneca Lake. The greater portion of the material consisted of copepods in Canandaigua and Seneca Lakes; in the former they comprised about 67 per cent of the total amount of crustacean material and in the latter about 79 per cent. In Cayuga Lake, however, about 72 per cent of the material consisted of the clado- ceran Bosmina. Of the cladoceran material in Canandaigua Lake in 1910, Daphnia retrocurva furnished about 30 times as much as Bosmina and about 4 times as much as Diaphanosoma. Bosmina was the only representative of this group that was obtained from the other two Finger Lakes in 1910. Among the copepods Diaptomus was the most important form in this year and Cyclops ranked second. In 1918 Canandaigua Lake possessed only about a third as much crustacean material as in 1910 and Cayuga Lake only about four-fifths as much. Seneca Lake, on the other hand, showed a much larger amount in the former year, the amount exceeding that of the latter year by about 62 per cent. ‘Thus Seneca Lake in 1918 had almost four times as much crustacean material as Canandaigua Lake and more than twice as much as Cayuga Lake. Daphnia retrocurva was again the chief cladoceran element in Canan- daigua Lake, but it was greatly exceeded by Bosmina in the other two lakes. Diaptomus furnished the largest amount of crustacean material in Canandaigua and Cayuga Lakes, but Cyclops was the chief constituent in Seneca Lake. Green Lake, Wis., possessed a larger amount of crustacean material in 1918 than was found in the three Finger Lakes either in 1918 or in r910.. It was almost 10 per cent greater than that of Seneca Lake in 1918, which was the maximum for the three Finger Lakes. The copepods formed a much larger proportion of the material in Green Lake than in the Finger Lakes, because the Cladocera constituted a little less than 3 per cent of the total in this lake. Nearly two-thirds of the entire amount of crustacean material in Green Lake was furnished by Diaptomus. Table 19 shows that the ash constitutes from 13 to 19 per cent of the dry weight of the crustacea of the Finger Lakes. In addition, also, it has been found that plankton crustacea contain from 4 to 9 per cent of chitin, which has no food value. In round numbers, then, it may be said that about 20 per cent of the dry weight of the plankton crustacea from the Finger Lakes consists of ash and chitin, while about 80 per cent may be regarded as actual food material. In the living state from 85 to 90 per cent of the mass of these organisms consists of water, so that the live weight would be ap- proximately 10 times as large as the figures given in the dry weight column of Table 20, page 248. In the crustacea from Green Lake the ash was much smaller, averaging somewhat less than 6 per cent; adding to this about 6 per cent for chitin leaves about 88 per cent of food material. ‘The latter figure is higher than that for the Finger Lakes, which is due to the higher percentage of ash in the material from these lakes. 240 BULLETIN OF THE BUREAU OF FISHERIES. No determinations of the weight of the rotifers were made for the Finger Lakes, but such results have been obtained for three species from Wisconsin lakes, namely, Asplanchna brightwellit, Brachionus pala, and Conochilus volvox. ‘The weight of ‘these forms has been used as a basis for estimating the weight of the various rotifers in the plankton catches from the three Finger Lakes, N. Y., and from Green Lake, Wis. The computations are based on the relative volumes of the different forms, so that they are to be regarded as estimates and not the results of actual weighings. These estimates are shown in Table 20. Cayuga Lake had the largest amount of rotifer material both in 1910 and in 1918, with 111 kg./km.? (1 pound per acre) in the former year and 145 kg. (1.3 pounds) in the latter year. It had 434 times as much as Seneca Lake in 1910 and about 3% times as much in 1918; it had 12 times as much as Canandaigua Lake in 1910 and about 52 times as much in r918. Green Lake had just half as much rotifer material as Cayuga Lake in 1918. In the rotifers that have been weighed the ash averaged about 7.4 per cent of the dry weight, ranging from a minimum of a little Jess than 6 per cent to a maximum of a little more than 9 per cent. Thus between go and 95 per cent of the dry weight of these rotifers may be regarded as organic matter, but what proportion of this is indigestible has not been determined. Also it has been found that from 90 to 94 per cent of the living rotifer consists of water, so that the weight of the live organisms would be somewhat more than 10 times as large as the figures given in the table. The relative importance of the crustacea and the rotifers as sources of organic matter which will serve as food for other organisms is shown in Table 20. In Canan- daigua Lake, which had a very small rotifer population, the ratio of the organic matter in the rotifers to that in the crustacea was 1:256 in 1910 and 1:292 in 1918. Owing to the very much larger rotifer population in Cayuga Lake the ratio there was 1:13 in 1910 and about 1:9 in 1918. In Seneca Lake these ratios were about 1:70 each year. In Green Lake the crustacea contributed about 49 times as much dry organic matter as the rotifers in 1918. The dry weight of the crustacea and rotifers combined amounted to 2,588 kg./km.? (23 pounds per acre) in Canandaigua Lake in 1910; this was the maximum quantity found in the three Finger Lakes in that year. The minimum amount was noted for Cayuga Lake, namely, 1,945 kg. (17.3 pounds). (See Table 20, p. 248.) In 1918 the maximum for these two groups of organisms was found in Seneca Lake and it amounted to 3,267 kg. of dry matter per square kilometer (29.1 pounds per acre). Canandaigua Lake possessed the minimum amount for this year, namely, about 852 kg. (7.6 pounds). This was only about one-third as much as this lake yielded in 1910. In Green Lake these two groups of plankton animals yielded about 3,458 kg. of dry matter per square kilometer of surface (31.6 pounds per acre) which was about 10 per cent larger than the amount in Seneca Lake in 1918. No attempt was made to determine the weight of the alge in the net plankton, but as the catches appeared under the microscope by far the greater portion of the mate- rial consisted of rotifers and crustacea, probably three-quarters of it or more. Adding 25 or even 50 per cent to the above figures would still leave a relatively small amount FINGER LAKES OF NEW YORK. 241 of material per unit of surface. In general, these lakes may be regarded as poor in net plankton, the usual characteristic of lakes as large and as deep as these. ‘The figures given in the various tables represent the amount of material that is present on a particular date—that is, the standing crop at that time—but they do not indicate the quantity of such material that is produced annually. Production and destruction are processes which continue throughout the year, so that it is a very difficult problem to ascertain just how much net plankton is produced annually by a lake. NANNOPLANKTON. The nannoplankton includes the various forms of plants and animals which are so small that they readily pass through the meshes of the bolting-cloth strainer in the plank- ton net and are lost. These small organisms are easily obtained with a centrifuge. The results obtained in these enumerations on the three Finger Lakes of New York and on Green Lake, Wis., are shown in Table 21. The Protozoa were represented by rhizopods, flagellates, and ciliates. The rhizo- pods consisted of Amoeba and some other forms which were not definitely identified. A minute Monas-like form was the most numerous flagellate found, while Cryptomonas was present in considerable numbers in Canandaigua and Seneca Lakes. A disk-shaped flagellate was noted in the upper strata of Cayuga and Green Lakes. Synura was also present in the surface stratum of Canandaigua Lake. The only representative of the ciliates was Halteria. It appeared in the upper strata of Canandaigua and Cayuga Lakes. The green and blue-green alga consisted of Scenedesmus, Oocystis, and Aphanocapsa. A colonial form composed of very minute cells, 25 to 100 or more, embedded in a gelat- inous matrix, has been referred to the genus Aphanocapsa. It appears to be widely distributed, geographically, since it has been found in all of the Wisconsin lakes from which nannoplankton has been obtained, and also in the three Finger Lakes. This alga has usually been fairly evenly distributed throughout the entire depth of the various lakes. This phytoplankton and the monads constitute the most common elements, numerically, of the nannoplankton. The water bacteria belong to this group of plankton organisms, but they were not taken into consideration in these investigations. No attempt was made to determine the amount of nannoplankton by weight, but some results that have been obtained'on Lake Mendota, Wis., will serve as a basis for making a rough estimate for the Finger Lakes. The studies on Lake Mendota covered a period of more than two years and they consisted of both gravimetric and numerical determinations. ‘The dry organic matter of the nannoplankton varied from a mini- mum of approximately 0.8 gr. to a maximum of 3.1 gr. per cubic meter of water. The numerical determinations which correspond most closely to those of the Finger Lakes average about 1.0 gr. of dry organic matter per cubic meter of water, so that this figure may be taken as a basis for estimating the amount of nannoplankton material in the latter. The results of this estimation are shown in Table 22, and also the results for total plankton. In the latter it has been assumed that the crustacea and rotifers furnished 75 per cent of the organic matter of the net plankton. Green Lake has not 242 BULLETIN OF THE BUREAU OF FISHERIES. been included in this table because its net plankton contained a larger percentage of vegetable material. These computations seem to indicate that the nannoplankton of Seneca Lake contained somewhat more than 234 times as much dry organic matter as the net plankton, while in Canandaigua Lake the former was more than 4 times as great as the latter. These differences are of the same magnitude as those that have been obtained on Lake Mendota in midsummer. On an average, also, it may be considered that this material weighs at least 10 times as much in the living state, since most of these organisms, when alive, are made up of 90 per cent or more of water. The results shown in this table represent only a single phase of the annual cycle, and hence they do not give any indication of the yearly production of such material. This latter question involves the actual turnover in stock each year and includes the various relations of the organisms to each other and to their environment; the chief phases of this question are the rate of reproduction of the various forms at different seasons of the year, and the relations of the consumers and their foods. The whole problem is very complex and would require an extended investigation for an adequate solution. These quantities of dry organic matter in the total plankton of the Finger Lakes are very much smaller than those that have been obtained for Lake Mendota, Wis., in midsummer. In this latter lake the average amount for the month of July in 1915 and in 1916 was 40,630 kg./km.? of surface (362.4 pounds per acre) in that portion of the lake having a depth of 20 m. or more; the average for August of these same years was 31,560 kg. (281.5 pounds). The average for Lake Mendota in July is more than three times the amount shown in this table for Seneca Lake and more than eight times that for Canandaigua Lake. Comparisons have been made between the productivity of the land and of the water, but such comparisons have been based upon the production of beef on the one hand and of fish, or oysters, or other edible aquatic forms on the other hand. These materials are what may be termed the “finished products,” and statistics relating to them give no idea of the relative amounts of food required or available for their pro- duction. This is accounted for by the fact that data concerning the quantity of food available, either directly or indirectly, for aquatic organisms have been for the most part wholly lacking and at best only fragmentary in character. The quantitative results given above for the plankton, however, enable one to make direct comparisons with the land on material which is not an end product. The grass produced by a pasture is probably the best land crop for such a comparison, be- cause it is less subject to artificial conditions resulting from cultivation than the grain crops. Henry (1898, p. 180) cites an experiment in which a pasture consisting of blue grass and white clover yielded 165,827 kg. of dry organic matter per square kilometer (1,477 pounds per acre) between May 1 and October 15. This quantity is just a little more than four times the average amount of organic matter maintained by the deeper water of Lake Mendota in July. In other words, a fourfold turnover in the stock of plankton maintained by Lake Mendota during this month would have yielded as much organic material annually as the pasture in the above experiment. During the vernal and autumnal maxima of the plankton the difference is distinctly less than fourfold. The roots were not included in this yield of grass and, taking them into consideration, FINGER LAKES OF NEW YORK. 243 we may say that the average difference for the year would be substantially fourfold. The differences are much greater in the Finger Lakes, ranging from about fourteenfold in Seneca Lake to almost thirty-fivefold in Canandaigua lake. (See Table 22, p. 250.) The dry organic matter of the grass was made up of about 25.4 per cent crude protein, 4.7 per cent ether extract, while the remainder consisted of carbohydrates. The plankton of Lake Mendota, however, was distinctly richer in nitrogenous material and in fats; the average for the crude protein was 45.1 per cent of the dry organic matter and for the ether extract 8 per cent. Attention should also be called to the fact that the plankton does not represent all of the food material that is produced by a lake; the bottom fauna and the large aquatic plants growing in the shallower water make notable contributions to this mate- rial. The quantity of plankton is not as large per unit of surface in the shallower water as it is in the deeper water, but the larger bottom population in the former region tends to counterbalance this deficiency when the question of the total production is con- sidered. PLANKTON TABLES. Tables 17 and 18 show the vertical] distribution of the various organisms consti- tuting the net plankton, giving the number of individuals per cubic meter of water in the different strata. The members grouped in the different columns are indicated as follows: CLapoceRA.—B=Bosmina, C=Ceriodaphnia, D=Daphnia, Di=Diaphanosoma, L=Leptodora, P=Polyphemus. Coprrpopa.—C=Cyclops, D=Diaptomus, E=Epischura, L=Limnocalanus. NAvpPLu. RotiFERA.—A=Asplanchna, A.a.=Anuraea aculeata, A.c.=Anuraea cochlearis, C=Conochilus, N=Notholca, P=Polyarthra, Pl=Ploesoma, R=Rattulus, S=Synchaeta, T=Triarthra. Protozoa.—A=Actinosphaerium, C=Ceratium, D=Dinobryon, E=Epistylis, M=Mallomonas, U=Uroglena, V=Vorticella. GREEN AND BLUE-GREEN ALGaAj.—An=Anabaena, Ap=Aphanocapsa, Coe=Coelosphaerium, G=Gloeocapsa, L=Lyngbya, M=Microcystis, O=Oscillatoria, S=Staurastrum. Diatoms.—A=Asterionella, F=Fragilaria, M=Melosira, S=Synedra, T=Tabellaria. TaBLE 17.—ANALYSIS OF NET PLANKTON, 1918. CANANDAIGUA LAKE, JULY 27, 1918. mn : Green and. Depth in meters. Cladocera. | Copepoda.| Nauplii. | Rotifera. | Protozoa. blug green Diatoms, alge. B 785 GC 5,376 || perccxnncnese D 1,830 13,470 U 13, 600 M 13,600 F 6,800 E 130 U 13,600 U 17,000 $ 10, 200 F 3, 400 244 BULLETIN OF THE BUREAU OF FISHERIES. TABLE 17.—ANALYSIS OF Net PLANKTON, 1918—Continued. CAYUGA LAKE, JULY 30, rorx8. Green and Depth in meters, Cladocera. | Copepoda.| Nauplii. | Rotifera. | Protozoa. plas treed Diatoms. alge. B 10, 200 C2008) ia aaaceienes ASOTG- IIx sass ceiesierats [teem ancaatsiaeal see ainee naeertes C5 Bi SBO: lhe i adevetens estsvie [venncas ahs woesonen sasnadeetan ocd BNE C 33,750 | A 108,800 | An 13,600 A 13,600 P17, 400 | C 129, 200 M 6, 800 F 20, 400 Pl. 150 |.. ‘ : S$ 25,770 |.. WAHT; 180: |seeseees a hee A... 4, 580 A 34,000 |............ A 27, 200 C 17, 265 102,000 M 6, 800 F 27,200 21,000 : Pl. 300 --| _ 337,400 -| A. ©. 3, 530 SENECA LAKE, AUG. 1, 1918. C 25, 100 |, L reOnbag &Soas el w FINGER LAKES OF NEW YORK. TaBLE 17.—ANALYSIS OF NET PLANKTON, 1918—Continued. GREEN LAKE, WIS., AUG. 20, 1918. 245 : Green and Depth in meters. . Cladocera. | Copepoda. | Nauplii. | Rotifera. | Protozoa. ae Diatoms. alge. B 1,570 © 86,868 Ih oy pavenenwrs C 5,100 C 20,400 | An 27,200 OS hacia eric cata a yale ndeminacis wamenienee D 302 D 33,225 87,900 N 3, rfo D 6,800 |O 1,822,400 |... Di 915 B 260 D 525 C8) 565) D 21, 715 ' P 2, 485 |.. . |A.e. 10,725 |.. Cors 7 TABLE 18.—ANALYSIS OF NET PLANKTON, IgI0. ‘ CANANDAIGUA LAKE, AUG. 20, rgr0. : Green and] __ Depth in meters. Cladocera. | Copepoda. | Nauplii. | Rotifera. | Protozoa. alteaet Diatoms. algae. B 260 C 4, 500 18, 500 C 130 Ap 11, 600 A. 34, 800 D 14, 200 |. ‘ uid F 3, 800 CHG ois Vee tin aceeeccjonia ¥4 SOME Re aS BP e va cmenaies che enwauarcnetemenas v4 soe Io-Is. Veet eeen ee eee reese Ce pebsicze Baath stardigtarsie T520.eeeeeeees a) Rie PeRanpa peoeaunennee BOZO cevccccvecvenneeeeseanveancrseres SO-40ins cenaneenns veneneneei ves shivecen ss Coe 3, 800 Lae 246 BULLETIN OF THE BUREAU OF FISHERIES. TaBLE 18.—ANALYSIS OF NET PLANKTON, rg10o—Continued. CAYUGA LAKE, AUG. 12, 1910. Green and : Depth in meters. Cladocera. | Copepoda. | Nauplii. | Rotifera. | Protozoa. Bing aieett Diatoms. alge. C 1, 648, 600 A 9,000 | A 2, 10s, 300 M 1, 000 F 812, yoo ag T 54, 200 ‘A 3, 204, 000 D 15, 500 M 7, 700 928, 800 W686 ove genitaanaa T 108, 300 C 665, 600 A 7, 700 | A 2, 182, 700 D 15,500 | M 31,000 F 944, 300 Vi 260 be osc. cnc T 123, 800 M 3, 800 T 27,000 F 7, 700 T 7, 700 An 1,900 M 7,700 A 310,700 F 5,800 FINGER LAKES OF NEW YORK. 247 TABLE 18.—ANALYSIS OF NET PLANKTON, rg910o—Continued. SENECA LAKE, AUG. 2, 19:0—Continued. : : Green and Depth in meters. Cladocera. | Copepoda.| Nauplii. | Rotifera. | Protozoa. | blue-green | Diatoms. alge. 00. M 9,600 Drso “ L 10 TABLE 19.—WEIGHTS OF DIFFERENT ForMS OF CRUSTACEA FROM THREE FINGER LAKES, N. Y., AND FROM GREEN LAKE, WIS. CANANDAIGUA LAKE. : Wet weight in Dry weight in Organism: milligrams. milligrams. Per cent.| Per cent. Remarks. = of water.| of ash. . Name. No. | Total. Each, Total. Each. Daphnia: sc. sc sewnivcaneaaiasca oie aceon -25 | 0.0230 |.......... 22.40 | Adults. Diaptomus.................665 id SA Bh 64 BOOB | rypiorsictsarers iets 13-41 : ‘ Limnocalanus it 14 MOBAS [scene vies 5.45 | Mixed sizes. MY Sissi 255 pst magninays i se aud Loan 20 | 1T00 |.....-.00. 12. 02 _ Do. BOSMING, ¢ ce caw sass eg cenewie os on gee +90 200296 |.........- 31.11 | Chiefly adults. Polyphemus............6: ee eee cece eee eee -78 JOLOI. | svrea Ya osx 21.80 | Mixed sizes. GOA. |aidscsiy eae oe OAS 1.89 | 0.0047 |.......... 12.70 | Chiefly adults. 250. raicxcusadee vuarsieats Gales Geaea 12-75 SORIO: fe os qe erases 3-78 | Large. $32 23- 46 0. 0441 2-34 +0044 90. 00 15-38 | Chiefly adults. SENECA LAKE Diaptomus.......... 60. cece eee teens 200 12.16 0. 0608 1.26 | 0.0063 89. 64 15. 08 Limnocalanus ..| 108 37°77 +3497 5-14 +0476 86. 40 6.61 q i Daphitia...... 0... ceed asda eee eee nee nes GOO. | viactcnernees acl ereadnes seein 2.56 POO§T |. oa dgnsiees 15.62 | Mixed sizes. GREEN LAKE. Diaptomus. ..........06 5. cee cnet ee eens BOO Neserey sa caveats aiceshaveisness 3:69 | 0.0074 |.......04. 5.15 | Chiefly adults. Limnocalanus G50 laces os oxste| soreness 17.88 20325? |lasuivaiynrars oie 3°75 248 BULLETIN OF THE BUREAU OF FISHERIES. TABLE 20.—DRY WEIGHT AND ORGANIC MaTTrER OF PLANKTON CRUSTACEA AND RotTIFERSIN THREE Fincer Laxes, N. Y., AND IN GREEN LAKE, WIS. CANANDAIGUA LAKE. IgIo 1918 Dry weight. ‘Organic matter. Dry weight. Organic matter. Organism. Kilograms Kilograms Kilograms Kilograms per square | Pounds | per square | Pounds | per square| Pounds | per square| Pounds kilometer | per acre. | kilometer | per acre. | kilometer | per acre. | kilometer | per acre. of surface. of surface. of surface. of surface. 15. 80 O14 27.70 0. 25 19. 10 O17 517.70 4. 61 94. 70 » 84 73. 50 65 154. 70 1. 38 16. 30 +14 15. 30 -13 182. 60 1. 62 38. 50 +34 33- 60 +30 I, 094. 15 9.74 385. 10 3-43 333- 50 3.00 158. 80 I. 42 271. 20 2.41 256. 40 2. 28 aufeaieneieangaesa: ee fies sa bstaxt bee 10. 10 09 9. 50 +08 72. 21 64 5. 30 +05 4.60 +04 2,195.96 19. 55 848. 90 7-55 745- 5° 6.65 8. 56 +074 2.76 024 2.55 022 CAYUGA LAKE. Plankton crustacea: Bosmina sciatic “ayd wiatayrsepretsasions 263202 000 I, 320. 25 11.75 909. 52 8.10 459- 43 4.09 316. 57 2. 82 Daphnia. ois consauincapies og alain aanveecios [oateuraewws la aiisrenners a3) eat es ian 14. 38 +13 II. 20 10 Cyclops. ee 155. 41 1. 38 135-67 I. 20 374. 61 3.33 327.00 2.90 Diaptomus. 2 ye is i 1.97 519. CO 4. 60 449. 40 4.00 Limnocalanus. ae 36. 13 +32 34-70 . 28 Natplitvads sai ssaseatwnieds sited 103. 06 «92 89. 66 68. 00 . 60 59. 20 +52 Total... cic cecee Rddsdaheyelenaie SiGe 1, 834. 14 16. 32 1, 356. OL 12.07 I, 471.55 13. 07 1, 198, 07 Io. 62 RROGHETS 9 2: f05-disipd deed aeindrnsiev 483 T10. 91 I.00 102. 78 +92 145. 24 1.30 134. 50 I. 20 SENECA LAKE. 421.00 3-75 290. 00 2. 60 16. 70 -14 13. 00 .10 I, 491. 60 13.30 I, 262. 00 II. 30 I, 192. 00 10. 60 I, O13. 20 9. 00 69. 00 . 61 64. 40 +57 35-70 +32 30. 30 +27 Totalasi cite dae pctniiaawnans 1, 992. 04 17. 72 1, 625. Bo 14. 45 3, 226. 00 28.72 2,672.90 23. 84 Rotilers: »:ixsaas a4 exe eeanesccaenss 24. 58 +22 22. 78 20 4r. 28 +37 38. 22 +34 GREEN LAKE. 24.00 oO. 21 22.44 oO. 20 59-35 +53 50. 00 +44 20. 60 «18 19. 30 +17 809. 00 7.20 760. 50 6. 80 2, 034. 31 18, 10 1, 929. 54 17.16 104. 20 +92 100. 30 - 88 424. 00 3:77 400. 68 3-55 Teta) schpaci du se Saviveesnet tate evacecal a esperar see olf eceve ecg nie tl Saale Besrendas [eeadoeanictinate st 3,475. 46 30. 91 3, 282. 76 29. 20 PROtHOTS ss ciandealerw lates wv resin Sictarcagretnave ale catatoeatelecs ate Lasraioe Mie viced lee etcemnigiantonces | monienineyen 92.70 65 67. 32 . 60 FINGER LAKES OF NEW YORK. 249 Table 21 shows the vertical distribution of the organisms 1n the nannoplankton, The forms are as follows: indicating the number of individuals per cubic meter of water at the different depths. Protozoa—A=Amoeba, C=Cryptomonas, F=unidentified asymmetrical flagellate, H=Halteria, M=monads,. R=unidentified thizopods, S=Synura, GREEN AND BLUE-GREEN ALGai—Ap=Aphanocapsa, Oo=Oocystis, Sc=Scenedesmus Diatoms—N=Navicula, S=Stephanodiscus, Sy=Synedra. TABLE 21.—ANALYSIS OF NANNOPLANKTON. CANANDAIGUA LAKE, JULY 28, r918. * Depth in Green and blue- . Depth in Green and blue- He meters. Protozoa. green alge. Diatoms. meters. Protozoa. green alga. Diatoms. B aee th eee C 31,242,000 | Ap 135,382,000 | ° 18,621,000 36 g { C 5,207,000 | AP 98,933,000 N 10, 414,000 Ph - See eucon cee four fl ee ee M 10,414,000 |........ec cece ees ape aec ieee : 57 200,000 Weise s eiciseiiaies neve] omnienrsives site IO, 414,000 C 10, 414,000 | Ap 182,245,000 S 36, 449, 000 || 30--++ +++ M 31,242,000 | Ap 130,175,000 K{ Ss 8830 008 Sows caw H. 5,200,000 |..........6.0- Sy 10,414, 000 C 15,621,000 | Ap 135,382,000 5) 207,000 ne ‘M_15,621,000 |....... gp bawail aaj easads wd Salads ADS ahneisitie rs M15 ,629;000'| .cccisejsie'ac oa acters : $ 10, 414,000 C 5,207,000 | Ap 187,452, . § 31,242,000 C 5,207,000 | Ap 130,175,000 $ 26,035,000 Piavigeces 5;200,000 |..... a5 Sy 5,207,000 M 20,484,000 | congeses vi enndeclorisasawen 2 asin Mi:20;:828; C000 fo -s:aicicie sina serivalliipiarteraes wayomnce.a- || OSs-cwrewadanlenuss Mastamaeisew AP 229, 108, 000 S 10, 414, 000 C 20,828,000 | Ap 156, 210, N ro, 414,000 WSacscicvves H 5; 200, 000 Sc 20, 828, 000 S 57,277,000 Mi 20;414/ 600i) ts duitetraster vn conalemmeanesshen ei 2 CAYUGA LAKE, JULY 30, 1918. F314 /242 000! |i axrcaxsias o4anevoleamanenne enya M 20,828,000 | Ap 62,484,000] _ $5,207,000 H_ 5,207,000 Ap 93, 726,000 N 5, 207,000 M 26,035,000} Ap 67,691,000 |- S 5,207,000 pies Onin piapititie M 26,035,000 Sc 20, 828, 000 S 5,207,000 M 26,035,000 | Ap 52,070,000 S 5,207, 000 R 20, 828. 15,621,000 | Ap 62,484,000 |.........5.. 0005 4 "26, 035, 000 { 10,414,000 | Ap 67,691,000 S 5,207,000 Geis dese M 20, 828, c00 R 5,207,000 |........ peaplaistese ¥10i8 es wild patneianessereats R 52,070, 000 i C 5,207,000 | Ap 78,105,000 |...........00 ee Bias wiesvacere M 36, 449, 000 Sc ro, 414,000 S 5,207,000 Re20;82850060) ss idscsccav ss saanlaswsim anise é SENECA LAKE, AUG. :, ror8. C 41,656,000 | Ap 72,898, 000 S 15,621, 000 C 5,207,000 | Ap 36,449,000 |........... 0.08 ie NUN Oeegetersesl\ ME 148, 800,000 Oo 5, 207,000 Sy 5,207,000 |] 30......... M 36,449,000 | O0 10,414, 000 S 10, 414, 000 C 15,621,000 | Ap 161,417,000 S 15,621,000 R520 7,900) [hers nas dissec visa erdrarall ne eoie bagsiaare ahaine: < Somes erp M 119,761,000 OO 10, 414,000 |.... 2. cece eee GOs vas tis se M 20, 828,000 | Ap 62, 484, 000 S 5,207,000 5,207,000 | Ap 62,484,000 S 15,621,000 || 75......... M 5,207,000 | Ap 72,898,000 10,414, 000 ROSES aires M 20, 828, c00 Oo 15,621, 000 M 15,621,000 | Ap 67,691,000 S 10, 414, 000 C 5,207,000 | Ap 67,691,000 M 10,414,000 | Ap 46,863, 000 S 5, 207,000 M 10,414,000 | Oo 26,035, 000 5,207,000 | Ap 67,691, 000 S 5,207,000 5,207,000 | Ap 36,449, 000 M 10,414,000 | Oo 10,414,000 GREEN LAKE, WIS., AUG. 20, 1918. Ey he rr S 5,207,000 |} 45 { M 20,828,000 | Ap 72,900,000 S 5,207,000 M ro, 414,000 | Ap 145, 800, 000 Sy 20,828,000 || ““"""'**** 57 QOT 000: oe oe tre-cicienpawiaae alle aaiere’s aarduiavaie’e a RR 55,207) 000: | ericcwiseiee ns ceanivicp anima as Rebar Owais ee neue M 5,207,000 | Ap 46,800,000 S 5, 207, 000 F 10, 414,000 | Ap 145,800, 000 S 5,207,000 |] 4, : { A 5,207,000 } ADP 57,200, 000 5) 207, 000 MM 86,44, 008 |i serayes cxveneceel., Sy 15,621,000 || T°" "777 ** _ _R5,207,000 |...... shpeecgecen! SY Spa07.000 15,621,000 | ADP 130, 200, 000 S 5,207,000 |} 50......... [ 5,207,000 | Ap 67, 700, IO, 414,000 M 26,035,000 |.........-000 0 eee Sy 15,622,000 |} 65......... M 5,207,000 | Ap 62, 500, 000 S 5,207,000 M 10,414,000 | Ap 52,070,000 Hp207,000 || eka amereaes exasl ena see VeNMew Sy 5,207,000 250 BULLETIN OF THE BUREAU OF FISHERIES. TABLE 22.—ESTIMATES FOR QUANTITY OF NANNOPLANKTON AND TOTAL PLANKTON IN THREE FINGER LAKES IN 1918. [Norx.—Total plankton equals net plankton plus nannoplankton. Quantities are shown in kilograms of dry organic material per square kilometer of surface and pounds per acre. Living material would weigh about 10 times as much as is indicated in the table.) Nannoplankton. Total plankton. Lake. ‘ : : “| Kilograms Pounds Kilograms Pounds per square | or acre. | Per sauare | oor acre kilometer. kilometer. Ss 3, 877.3 34.5 4, 809. 2 42.8 5, 450.0 48.5 6, 947.5 61.6 8, 859. 4. 78.8 12, 200. 5 108. 6 BOTTOM FAUNA. Samples of the bottom at different depths were obtained in the three Finger Lakes and also in Green Lake by means of an Ekman dredge. ‘This mud was sifted through a fine meshed net and the organisms found therein were enumerated. The dry weight and the ash of four of these bottom forms were ascertained. ‘The results of these dredge hauls are shown in Table 23. The observations were far too few in number to give anything more than a fragmentary idea of the density of the bottom fauna, since only two hauls each were made in Canandaigua and Cayuga Lakes and but four in Seneca Lake; in addition to this they were taken only in the deeper water. Hundreds, or better still, thousands of observations, covering the bottom of each lake in various places from the shore line to the greatest depths and extending through the different seasons of the year, would be necessary to give an adequate idea of the character and abun- dance of their bottom fauna. Only four forms have been included in the table because they constituted by far the greater portion of the material obtained. A few nematodes and an occasional estracod and bivalve mollusk were noted in the shallower depths, but they were not present in sufficient numbers to obtain their weights. A few larve of Protenthes were obtained in the 32 m. haul in Seneca Lake and in the 45 m. haul in Green Lake, but these were the only instances in which this larva was noted. Chironomid larve were found in all of the hauls except the one made at 32 m. in Seneca Lake. They were most abundant in Cayuga Lake, where they constituted by far the most numerous form at a depth of 113 m. In the other three lakes, however, they formed only a minor element of the bottom population, both in numbers and in bulk. Earlier in the season they were probably more numerous, because many had undoubtedly transformed to the adult stage by the time these observations were made. In Canandaigua and Seneca Lakes the relict amphipod Pontoporeia was second in importance, while it was third in Cayuga Lake and first in Green Lake. It was most abundant at a depth of 45 m. in Green Lake, where it furnished the largest amount of dry organic material that was found in any of the hauls, namely, about 8,214 kg./km.?, or nearly 75 pounds per acre. Oligocheta were found in all except one haul; that is, the one at 34 m. in Cayuga Lake. In half of the hauls they furnished the greater portion of the organic material. FINGER LAKES OF NEW YORK 251 The largest amount was obtained at 32 m. in Seneca Lake, where it reached 1,693 kg. of dry material per square kilometer, or a little more than 1 5 pounds per acre. The deepest haul in Cayuga Lake yielded a larger amount of organic matter than the deepest haul in any of the other lakes, while the one at 34 m. was the poorest of all, due most probably to the fact that it was made on a very steep slope. Green Lake showed the second largest amount of material in its deepest water and Canandaigua Lake was third. In Seneca Lake the amount at 110 m. was only about three-quarters as great as at 172 m. In general, it appears that the bottom fauna in the deeper water of Green Lake yields a larger amount of dry organic matter per unit area than these three Finger Lakes. : TABLE 23.—NUMBER OF INDIVIDUALS AND WEIGHT OF Bottom Fauna OBTAINED AT DIFFERENT DEPTHS IN THREE FINGER LAKES, N. Y., AND IN GREEN LAKE, WIS., IN 1918. CANANDAIGUA LAKE, JULY 28, 1918. Number Dry weight. Organic matter. - per Depth in ‘ mele: Organism. . | getter or | Kilograms | Pounds | Kilograms | Pounds bott per square per per square per ortom. | kilometer.| acre. | kilometer. | acre. (Chironomus 800 219.2 1-95 155-0 1.38 BOs sicasisite Pontoporeia.. . ‘ 977 469-0 4:17 352-0 3-13 Oligochaeta. .. 1,420 522-9 4-65 459-1 4.08 (Chironomus... fs 12.0 . aS 8. § +07 sdsyoee oie Pontoporeia... ‘ 44, 405-1 3-60 303- 2.70 s Oligochasta ecasngath-dvs acca neiGestorssdvecguans hauatenetator giv oh¥ dvetagetdenctaqepeiasaoe daa 890 326-8 aor 286.9 2.55 CAYUGA LAKE, JULY 30, 1018. 133 36.4 +33 25.7 +23 178 85.4 76 64.0 +57 3, 863 1,058. 9: 42 784-4 6.66 710 340.8 3-03 255-6 2.24 1,288 474-0 4-92 416.2 3-70 * SENECA LAKE, AUG. 4, 1918. Protentthes ..cijceieic's sidearm Wa cate saanaiaeis senna aemiee 89 gia -28 28.8 26 BP. cece ee a 1,110 532-8 4-74 399-6 3°55 Oligochaeta... 5,240 1,928.0 17.16 1,692.8 15-07 47 . J Chironomus. .. 577 158.0 1.40 IIle7 +99 co Pontoporeia . 844 405. x 3-60 303-8 2.70 Oligochaeta. 1,330 489-4 4°35 429-7 3-84 Chironomus. 444 120.6 1.07 85.3 ~76 TIO... eee Pontoporeia. 355 170.4 1.52 127.8 1.14 Oligochaeta. 400 147.2 1.31 14g. 2 1.15 (Chironomus. 44 12.0