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Author: 
 
 Vose, George Leonard 
 
 Title: 
 
 Bridge disasters in 
 America 
 
 Place: 
 
 New York 
 
 Date: 
 
 1880 
 
^^-^^\o>^ -g? 
 
 MASTER NEGATIVE « 
 
 COLUMBIA UNIVERSITY LIBRARIES 
 PRESERVATION DIVISION 
 
 BIBLIOGRAPHIC MICROFORM TARGET 
 
 RESTRICTIONS ON USE: 
 
 ORIGINAL MATERIAL AS FILMED • EXISTING BIBLIOGRAPHIC RECORD 
 
 •530.3 
 V92 
 
 Vose, George Leonard, 18S1- 
 
 Bridge disasters in Amerioat the cause and 
 the remedy. New York, The Railroad gatette, 
 1880. 
 
 30 p. 20om. 
 
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 THE LIBRARIES 
 
 SCHOOL OF BUSINESS 
 
I 
 
 BRIDGE DISASTERS 
 
 • IN 
 
 ^MEKICA.: 
 
 THE CAUSE AND THE REMEDY. 
 
 BT PROFESSOR GEORGE L. VOSE. 
 
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 PUBLISHED B\' "ME RA'LROAO GAZETTE. 
 
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 >■•( 
 
 BRIDGE DISASTERS IN AMERICA. 
 
 THE CAUSE AJS^D XHE REJMEIDY. 
 
 A few years ago an iron highway bridge at Dixon, 111., 
 fell, while a crowd was npon it, and killed sixty persons. 
 The briefest inspection of t. .t bridge by any competent en- 
 gineer would have been sure to condemn it. A few years 
 later the Ashtabula bridge, upon the Lake Shore Railroad, 
 broke down under a passenger train, and killed from 80 to 
 100 passengers. The report of the committee of the Ohio 
 Legislatm-e appointed to investigate that disaster concluded, 
 first, that the bridge went down under an ordinary load by 
 reason of defects in its original construction ; and, secondly, 
 that the defects in the original construction of the bridge 
 could have been discovered at any time after its erection by 
 careful examination. Hardly had the public recovered 
 from the shock of this terrible disaster when the Tariffville 
 calamity added its list of dead and wounded to the long 
 roll already charged to the ignorance and recklessness which 
 characterizes so much of the management of the public 
 works ill this country. 
 
 There are many bridges now in use upon our railroads in 
 no way better than those at Ashtabula and Tariffville, and 
 which await only the right combination of circumstances to 
 tumble down. There are, by the laws of chance, just so 
 many persons who are going to be killed on those bridges. 
 There are hundreds of highway bridges now in daily use 
 which are in no way safer than the bridge at Dixon was, 
 and which would certainly be condemned by five minutes of 
 competent and honest inspection. More than that, many of 
 them have already been condemned, as unfit for public use, 
 but yet they are allowed to remain, and invite the disaster 
 which is sure to come. Can nothing be done to prevent this 
 reckless and wicked waste of human life ? Can we not have 
 some system of public control of public works which shall 
 secure the public safety « The answer to this question will 
 
"^MmK 
 
 be, not until the public is a good deal more enlightened upon 
 these mattei'8 than it is now. 
 
 It has been very correctly remarked that in order to bring 
 a disaster to the public notice it must be emphasized by loss 
 of life. The Ashtabula bridge fell and killed over 80 per- 
 sons, and a storm of indignation swept over the country 
 from one end to the other. No language was severe enough 
 to apply to the managers of the Lake Shore Railroad; but 
 if that very bridge had fallen under a freight train, and no 
 one had been injured, the occurrence would have been dis- 
 missed with a paragraph, if, indeed, it had received even 
 that recognition. In February, 1879, a span 110 ft. long 
 of an iron bridge on the Chicago & Alton Railroad, at Wil- 
 mington, 111., fell as a train of empty coal cars was passing 
 over it, and three cars were precipitated into the river, a 
 distance of over 30 ft.. No one was injured. Not a 
 word of comment was ever made in regard to this occur- 
 rence. Suppose that in place of empty coal cars the 
 train had consisted of loaded passenger cars, and that 100 
 persons had been killed. We know very well what the 
 result would have been. Is not the company just as much 
 to blame in one case as in the other ? On the night of 
 the 9th of November last one span of the large 
 bridge over the Missouri River, at St. Charles, upon the St. 
 Louis, Kansas City & Northern Railway, gave way as a 
 freight train was crossing it, and 17 loaded stock cars and 
 the caboose fell, a distance ©f 80 ft., into the river. Two 
 brakemen and two drovers, who were in the caboose, were 
 killed. The bridge, says the only account that has appeared, 
 did not break, apparently, for the whole span went down 
 with the cars upon it It could hardly make much difference, 
 we should suppose, to the four men who were killed, whether 
 tiie bridge broke down or went down. This disaster occurred 
 early last November, and not a word has appeared in the 
 papers since in regard to it. Suppose that in place of 17 
 stock cars half-a-dozen passenger cars had fallen from a 
 height cf 80 ft. into the river, and that in place of killing 
 two brakemen and two drovers two or three hundred pas- 
 sengers had been killed. Is not the general public just as 
 concerned in one case as the ot^er ? 
 
 Suppose that a bridge now standing is exactly as unsafe as 
 the Ashtabula bridge was the day before it felL Would 
 it be possible to awaken public attention enough to 
 have it examined ? Probably not. A short time since the 
 
 writer endeavored to induce one of the leading dailies in 
 Massachusetts to expose a wi*etchedly unsafe bridge in New 
 England ; but the editor declined on the ground that the mat- 
 ter was not of sufficient interest for his readers ; but less 
 than a month afterward he devoted three columns of his pa- 
 per to a detailed account of a bridge disaster in Scotland, 
 and asked why it was that such things must happen, and if 
 there was no way of determining in advance whether a 
 bridge was safe or not. This editor certainly would not 
 maintain that, in itself, it was more important to describe a 
 disaster after it had occurred, than to endeavor to prevent 
 the occurrence ; but, as a business man, he knew perfectly 
 well that his patrons would read an account giving all of the 
 sickening detail of a terrible catastrophe, while few, if any, 
 would wade through a dry discussion of the means for pro- 
 tecting the public from just such disasters. The public is al- 
 ways very indignant with the effect, but does not care to 
 trouble itself with the cause ; but the effect never will be 
 prevented until the cause is controlled, and the sooner the 
 public understands that the caiise is in its own hands, to be 
 controUed or not, as it chooses, the sooner we shall have a 
 remedy for the fearful disasters which are altogether too 
 <K>mmon in the United States. 
 
 In a country where government controls all matters on 
 which the public safety depends, and where no bridge over 
 which the public is to pass is allowed to be built except after 
 the plans have been approved by competent authority, where 
 no work can be executed except under the rigid inspection of 
 the best experts, nor opened to the public until it has been 
 officially tested and accepted, it makes little or no difference 
 whether the public is informed or not upon these matters; 
 but in a coimtry like the United States, where any man may 
 at any time open a shop for the manufacture of bridges, 
 whether he knows anything about the business or not, and is 
 at liberty to use cheap and insufficient material, and where 
 public officers are always to be found ready to buy such 
 bridges simply because the first cost is low, and to place them 
 in the public ways, it makes a good deal of 
 difference. There is at present in this country absolutely 
 no law, no control, no inspection, which can prevent the 
 building and the use of unsafe bridges ; and there never 
 will be until the people who make the laws see the need of 
 «uch control. There is no one thing more important in this 
 matter than that we should be able to fix precisely the re- 
 
sponabUity, ,n case of disaster, upon some per»o„ to whom 
 the proper punishment may be appUed. l" even- mUwav 
 Arector ortown or county officer, knew that he w™ he'd 
 personally accountable for the failure of any bnd« n 2f 
 
 structures^ If we could show that a certain bridge in a lar« 
 town had been tora longtime, old, rotten, , om-outi^nd li^ 
 
 that the public officers having charge of such a bridge toew 
 this t» be the case, and still aUowed the public to pa^ ove^T 
 
 a^d^Mv!^'n f '"""'" ""• *"»«8^ would be short 
 
 and decisive. Once let a town have heavy damages to oav 
 and let it know at the same time that thTtowrofflcl„'^S 
 clearly accountable for the loss, and it is Dossible Tl.7.^ 
 would be wiUing to adopt some system tilt T^d ^^n 
 the recurrence of guch an outlay. prevent 
 
 To see what may be accomplished by an efficient system 
 regard to the stinictures to oe inspected. We have now i^ 
 
 r.^ITrid.^'' T-'^y-botruponour^^'dTaTo.^ 
 nuiroads, bndges made entirely of iron, bridges of wood and 
 mm combmed, and occasionally, though noroften^w™ 
 days, a bndge entirely of wood; and thL struck .^ to 
 be seen of a great variety of patterns, of aU siJTa^iu 
 eveiT Stage of pr^rvation. America; enginir^'e ,i 
 w^exceUed in this branch of their busing Utoguns^-" 
 P«»ed by any other m.tion. Of late years, so ^at hJC 
 the demand for bridge work that this brai^ch o^ngin" r^° 
 h« become a trade by itself, and we Bnd immenTToX 
 
 ^Zt^" mUh'" T'T "™*y<" ""« "ostadm^iw; 
 adapted machine tools, devoted exclusively to the 
 
 matang ^ bridges „f w«k., i„„. steel, or' alf cc^m! 
 
 -thiss^al.Ttion'i'as ^Trim^ive' 'X 'th: ^^tt 
 of the preduct, to lessen the c«t, and to increase the de^^ 
 
 of these wretched traps do not tumble down, and cause a 
 greater or less loss of life; and at the same time, with unin- 
 formed people, throw discredit on the whole modern sys- 
 tem of bridge-building. This evil affects particularly 
 highway bridges. The ordinary county commissioner 
 or select-man considers himself amply competent to 
 contract for a bridge of wood or iron, though 
 he may never have given a single day of thought to the mat- 
 ter before his appointment to office. The result is that we 
 see all over the country a jjreat number of highway bridges 
 which have been sold by dishonest builders to ignorant offi- 
 cials and which are on the eve of falling, and await only an 
 extra large crowd of people, a company of soldiers, a pro- 
 cession, or something of the sort to break down. 
 
 After a defective bridge falls it is in nearly every case easy 
 to see why it did so. It would be just about as easy to tell 
 in advance that such a bridge would fall if it ever happened 
 to be heavily loaded. Hundreds of highway bridges are to- 
 day standing simply because they never happen to have re- 
 ceived the load which is at any time liable to come upon 
 them. 
 
 Not many years ago a new highway bridge of iron was 
 to be made over a broad river in one of the largest towns in 
 New England. The county commissioners desired a well- 
 known engineer, especially noted as a bridge-builder, to 
 superintend the work, in order to see that it was properly 
 executed. The engineer, after inspection of the plans, told 
 the commissioners plainly that the design was defective, and 
 would not make a safe bridge ; and that unless it was 
 materally changed he would have nothing to do with it. 
 The bridge, however, was a cheap one, and as such com 
 mended itself to the commissioners, who proceeded to have 
 it erected according to the original plan ; and these same 
 commissioners now point to that bridge, which has not yet 
 fallen, but which is liable to do so at any time, as a complete 
 vindication of their judgment, so called, as opposed to that 
 of the engineer who had spent his life in building bridges. 
 
 An impression exists in the minds of many persons that 
 an iron bridge is necessarily a strong bridge. This is a great 
 mistake. There are good iron bridges and there are also very 
 poor ones. A good iron bridge is the best bridge one can buy ; 
 but a poor iron bridge is the worst — ^much worse than a poor 
 wooden one; for when an iron bridge falls it is apt to go all 
 at once, but> wooden one shows signs of failure long before 
 
8 
 
 it actually gives way. Another fallacy which infests 8ome 
 persons is the notion that it is purely a matter of opinion 
 whether a bridge is safe or not. In nine cases out of ten it 
 IS not at all a matter of opinion, but a matter of fact and 
 of arithmetic. The whole question always comes to this: 
 Is the material in this bridge of good quality, is there 
 enough of It, is it property put together ? With given di- 
 mensions, and knowing the load to be carried, it is a matter 
 of the very simplest computation to fix the size of each 
 member. We know what one square inch of iron will hold 
 and we also know total the number of pounds to be sustained- 
 and It IS no matter of opinion, but one of simple division, aJ 
 to how many times one will go into the other. 
 
 But, it may be asked, can the precise load which is coming 
 upon any structure be exactly fixed ? Are not the circum- 
 stances under which bridges are loaded very different ? 
 Bridges in different localities are certainly subjected to very 
 different loads, and under very different conditions; never- 
 theless, the loads to be provided for have been fixed by the 
 best authority for all cases, within narrow enough limits for 
 all practical purposes. Few persons are aware of the weight 
 of a closely packed crowd of people. Mr. Stoney, one of 
 the best authorities, packed 30 persons upon an area of 29,% 
 square feet, and at another time he placed 58 persons upon 
 an area of 57 square feet. In the first case, the re- 
 sult was a load of 149 lbs. per square foot, and 
 m the second case a load of 147,*, lbs. per foot 
 Such cramming," says Mr. Stoney, " could scarcely occur 
 in Dractice, except in portions of a strongly excited crowd- 
 but I have no doubt that it does occasionally so occur." 
 " In my own practice," be continues, " I adopt 100 lbs. p^r 
 square foot as the standard working lead, distributed uni- 
 formly over the whole surface of a public bridge, and 140 
 lbs. per square foot for certain portions of the structure- 
 such for example as the foot-paths of a bridge crossings 
 navigable river in a city, which are liable to be severely 
 tried by an excited crowd during a boat-race, or some simi- 
 lar occasion." Tredgold and Rankine estimate the weight of 
 a dense crowd at 180 lbs. per square foot. Mr. Brunei used 
 100 lbs. m his calculations for the Hungerford Suspension 
 Bridge. Mr. Drewry, an old but exceUent authority, ob- 
 serves "that any body of men marching in step at from 3 
 to 3K miles an hour wiU strain a bridge at least as much as 
 double the same weight at rest;" and he adds: " In prudence 
 
 9 
 
 not more than one-sixth the number of infantry that would 
 fill a bridge should be permitted to march over it in step." 
 Mr. Roebling says, in speaking of Niagara Falls Railroad 
 Suspension Bridge: '* In my opinion, a heavy train, i-unning 
 at a speed of twenty miles an hour, does less injury to the 
 structure than is caused by twenty heavy cattle under full 
 trot. Public processions, marching to the sound of music, or 
 bodies of soldiers keeping regular step, will produce a still 
 more injurious effect." 
 
 Evidently a difference should be made in determining the 
 load for London Bridge and the load for a highway bridge 
 upon a New England country road in a thinly settled district. 
 A bridge that is strong enough is just as good and just as 
 safe as one that is ten times stronger, pnd even better; for 
 in a large bridge, if we make it too strong, we make it at the 
 same time too heavy. The weight of the structure itself has 
 to be sustained, and this part of the load is a perpetual drag 
 on the material. In 1875, the American Society of Civil 
 Engineers, in view of the repeated bridge disastei*s in this 
 country, appointed a committee to report upon " The Means 
 of Averting Bridge Accidents." We might expect, when a 
 society composed of some hundreds of our best engineers 
 selects an expert conmiittee of half a dozen men, that the 
 best authority would be pretty well represented, and such 
 was eminently the case. It would be impossible to have 
 combined a greater amoimt of acknowledged talent, both 
 theoretical and practical, with a wider and more valuable 
 experience, than this committee possessed. The first point 
 taken up in the report is the determination of the loads for 
 which both railroad and highway bridges should be propor- 
 tioned. In regard to highway bridges, a majority of the 
 coDunittee reported that for such structures the standard 
 loads should not be less than as shown in the following 
 table: 
 
 ^Pounds per Square foot.— v 
 Span. Class A. Class B. Class C. 
 
 00ft. and leM 100 100 70 
 
 eoto 100ft 90 76 60 
 
 100 to 200 ft... » 75 aO 50 
 
 200to400ft eO 80 40 
 
 Class A includes city and suburban bridges, and those over 
 large rivers where great concentration of weight is possible ; 
 Class B denotes higbway bridges in manufacturing districts, 
 having well ballasted roads; and Class C refers to ordinary 
 country road bridges, where travel is less frequent and 
 lighter. A minority of the committee modified the table 
 
10 
 
 above by putting all highway bridges into the first class 
 and by making the loads larger by a smaU amount. The 
 whole committee agreed in making the load per square foot 
 less as the span is greater, which is of course correct. It 
 would seem eminently correct to make a difference between 
 a bridge which carries the continuous and heavy traffic of a 
 large city and one which is subjected only to the compara- 
 tively hght and infrequent traffic of a country road. At the 
 same time it should not be forgotten that in a large part of 
 the Umted States a bridge may be loaded by ten, twenty or 
 even thirty lbs. per square foot by snow and ice alone, and 
 that the very bridges which from their location we should be 
 apt to make the lightest are those which would be most 
 iikely to be neglected, and not relieved from a heavy 
 accumulation of snow. In view of the above, and remem- 
 bering that a moving load produces a much greater strain 
 upon a bridge than one which is at rest, we may be sure 
 that, as the committee above referred to recommend, the 
 loads should not be less than those given in the table. We 
 can easily see that in special cases they should be more. 
 
 There is another point in regard to the loading of a high- 
 way bndge which is to be considered. It often happens 
 that a very heavy load is carried over such bridges upon a 
 single truck, thus throwing a heavy and concentrated load 
 upon each point as it passes. Mr. Stoney states that a wagon 
 with a crank shaft of the British ship Hercules, weighing 
 about 45 tons, was refused a passage over Westminster iron 
 bndge, for fear of damage to the structure, and had to be 
 earned over the Waterioo Bridge, which was of stone, and 
 he says that m many cases large boilers, heavy forgiugs or 
 castings, reach as high as 12 tons upon a single wheel. The 
 report of the American Society of Engineers, above referred 
 to, advises that the floor system be strong enough to can-y 
 the following loads upon four wheels: on Class A, 24 tons; 
 Uass B, 16 tons, and Class C, 8 tons; though it is stated that 
 these do not include the extraordinary loads sometimes taken 
 over highways. - This provision for local loads," says Mr. 
 iioller, one of the committee, " may seem extreme, but the 
 jar and jolt of heavy springless loads conies directly on all 
 parts of the flooring at successive intervals, and admonishes 
 us that any errors should be on the safe side." 
 
 To pass now to raiht)ad bridges, we find here a very heavy 
 load coming upon the structure in a sudden and often very 
 violent manner. Experiment and observation both indicate 
 
 11 
 
 that a rapidly-moving load produces an effect equal to 
 double the same load at rest. This effect is seen much more 
 upon short bridges, where the moving load is large in pro- 
 portion to the weight of the bridge, than upon long spans, 
 where the weight of the bridge itself is considerable. The 
 actual load upon a short bridge is also more per foot than 
 upon a long one, because the locomotive, which is much 
 heavier than an equal length of cars, may cover the whole 
 of a short span, but only a part of a longer one. The largest 
 engines in use upon our railroads weigh from 75,000 to 
 80,000 lbs. on a wheel-base not over 12 ft. in length, or 
 2,800 lbs. per foot for the whole length of the engine, and 
 from 20,000 to 24,000 lbs. on a single pair of wheels. The 
 heaviest coal trains will sometimes weigh nearly a ton per 
 lineal foot, the oi'dinar}' freight trains from 1,600 to 1,800 
 lbs., and passenger trains from 1,000 to 1,200 lbs. per foot. 
 Any bridge is liable to be traversed by two heavy 
 freight engines, followed by a load of a ton to the foot, so 
 that if we proportion a bridge for 3,000 lbs. per foot, for the 
 total engine length, and for a ton per foot for the rest of the 
 bridge, bearing in mind that 80,000 lbs. may come upon any 
 12 ft. of the track, and that any one point may be called 
 upon to sustain 24,000 lbs., and regarding the increase of 
 strain on short spans due to high speeds, we have the follow- 
 ing loads for different spans, exclusive of the weight of ^he 
 bridge : 
 
 Span. Lbs. per foot. Span. Lbs. per foot. 
 
 12 7,000 50 3,000 
 
 15 6.000 I 100 ;j,800 
 
 20 4,800 200 2,600 
 
 25. 4,000 300 2,500 
 
 30 3,600 t 400 2,450 
 
 40., 3,200 !500 2,400 
 
 The above does not vary essentially from the English 
 practice, and is substantially the same as given by the Com- 
 mittee of the American Society of Civil Engineers. 
 
 The load which any bridge will be required to carry being 
 determined, and the general plan and dimensions fixed, the 
 several strains upon the different members follow by a sim- 
 ple process of arithmetic, leaving to be determined the actual 
 dimensions of the various parts ; a matter which depends 
 upon the power of different kinds of material to resist differ- 
 ent strains. This brings us to the exceedingly important 
 subject of the nature and strength of materials. 
 
 It has been said that we know what one square inch of iron 
 will hold. Like the question of loads, above examined, this 
 
 f '■ 
 
■■■Ml 
 
 l'':i 
 
 12 
 
 is a matter which has been settled, at any rate wlthhi very 
 narrow limits, by the experience of years of both European 
 and American engineers. A bar of the best wrou^ht-iron, 
 one inch square, will not break under a tensile strain of less 
 than 60,000 lbs. Only a smaU part of this, however, is to 
 be used in practice. A bar or beam may be loaded with a 
 greater weight, applied as a permanent or dead load, than 
 would be safe as a moving or roUing weight A load may 
 be brought upon any material in an easy and gradual man- 
 ner so as not to damage it, while the same load could 
 not be suddenly and violently applied without injury 
 The margin for safety should be greater with a material lia- 
 ble to contain hidden defects than with one which is not so: 
 and it should be greater for any member of a bridge which 
 is subjected to several different kinds of strain than for one 
 which has to resist only a single- form of strain. Respect 
 also should be had to the frequency with which any part is 
 subjected to strain from a moving load, as this will mani- 
 festly influence its power of endurance. The rule in struc- 
 tures having so important an office to perform as raih-oad or 
 highway bridges, should be, in all cases, absolute safety 
 under all conditions. 
 
 The British Board of Tn»de fixes the greatest strain that 
 shaU come upon the material in a wrought-iron bridge from 
 the combined weight of the bridge and load, at 5 tons per 
 square mch of the net section of the metal. The French 
 practice allows 3^, tons per square inch of the gross section 
 of the metal, which, considering the amount taken out by 
 nvet holes, is substantially the same as the English allow- 
 ance. The report of the American Society above referred 
 to recommends 10,000 lbs. per inch as the maximum for 
 wrought-iron in tension in raili-oad bridges. For highway 
 bridges, which are not subjected to such severe treatment 
 a unit strain of 15,000 lbs. per square inch is often allowed.' 
 A very common clause in a specification is that The Factor of 
 S ifety shaU be four, fi veor six,as the case may be, meaning by 
 this that the actual load shall not exceed one fourth, one-fifth 
 or one-sixth part of the breaking load. It is a little unfor- 
 tunate that this term, "factor of safety," has found its way 
 mto use just as it has, for it by no means indicates what is 
 mtended, or what it is supposed to. The true margin for 
 safety is not the difference between the working strain and 
 the breaking strain, but between the working strain and that 
 strain which will in any way unfit the material for use. Now 
 
 18 
 
 any material is unfitted for use when it is so far distorted by 
 overstraining that it cannot recover, or, technically 
 speaking, when its elastic limit has been exceeded. 
 The elastic limit of the best grades of iron is just about 
 one-half the breaking weight, or from 85,000 to 30,000 lbs. 
 per square inch ; so that the working strain of 10,000 lbs. per 
 inch gives a factor of safety of two and a half or three, in- 
 stead of six. If the ratio between the elastic limit and the 
 breaking weight, t. e., if the quality of the iron was always 
 the same, it might make no great difference how we used our 
 factor ; but some iron is hard and brittle, while other iron is 
 soft and ductile. A high breaking strength may be due to 
 the toufi:hness of the iron, or to the hardness of the iron. A 
 soft and ductile iron will stretch more or less before bteak- 
 ing, while a hard iron will often snap short 
 off without warning, and at the same time 
 both may have the same breaking strength. A tough 
 and ductile iron should bend double when cold without show- 
 ing any signs of fracture, and should stretch 15 per cent, of 
 its length before breaking ; but much of the iron used in 
 bridges, although it may hold 50,000 lbs. per inch before 
 failing, will not bend over 90 degrees without cracking, and 
 has an elastic limit as low as 18,000 lbs. It is thus full as 
 important to specify that an iron should have a high elastic 
 limit, as that it should have a high breaking weight. A 
 specification therefore which allowed no material to be 
 strained by more than 10,000 lbs. per inch, and no iron to 
 be used with a less elastic limit than 25,000 lbs., would at 
 the same time agree with the standard requirement both in 
 England and in the United States, and would also secure a 
 good quality of iron. 
 
 The writer has before him two documents which illustrate 
 the preceding remarks. The first Is the account of the tests 
 of the iron which came from the Tariffville bridge after its 
 failure, and the second is the specification for the bridges 
 upon the Cincinnati Southern Railway. The Tariffville 
 bridge, though nominally a wooden one, like most structures 
 of the kind relied entirely upon iron rods to keep the 
 woodwork together. Though the rods were too small, 
 and seriously defective in manufacture, the bridge ought 
 not to have fallen from that cause. The ultimate strength 
 of the iron was not what it should have been, but yet it was 
 not low enough to explain the disaster; but when we look at 
 the quality of the iron we have the cause of the fall. The 
 
.-5*5 IP 
 
 ■■■i 
 
 14 
 
 rods taken from the bridge show an ultimate tensile strength 
 per square inch of 47,5t50 lbs., but an elastic limit of only 
 19,000 lbs., while the strain which was at any time liable to 
 come upon them was 23,000 lbs. per square inch, or 3,000 
 lbs. more than the elastic hmit. The fracture of the tested 
 rods, which it is stated broke with a single blow of the ham- 
 mer very much in the manner of cast-iron, show a very in- 
 ferior quality of material. The rods broke in the bridge ex- 
 actly where we should look for the faUure, viz. in the 
 screw, at the end. No ordinary inspection wonld have de- 
 tected this weakness. No inspection did detect it; but a 
 proper specification, faith fuUy carried out, woiUd have pre- 
 vented the disaster. 
 
 Look now at an extract from the specification for bridges 
 upon the Cincinnati Southern Railway : 
 
 *' AH parts of the bridges and trestle-works must be nro- 
 x)rtioned to sustain the passage of the following rolling 
 oad, a^ a speed of not less than 30 miles an hour, viz : two 
 ocomotives, coupled, each weighing 36 tons on the drivers 
 ma space of 12 feet, the total weight of each engine and 
 tender loaded being 66 tons in a sjmce of 50 feet, and fol- 
 J^^ ?^' loaded cars weighing 20 tons each in a space 
 of 22 feet. An addition of 25 per cent, will be made 
 to the strains produced by the rolling load considered 
 as static, m all i>arts which are liable to be thrown 
 suddenly under strain by the passage of a rapidly 
 moving load. A similar addition of 50 per cent. wiU 
 be made to the strain on suspension links and riveted con- 
 nections of stringers with floor-beams, and flooi-beams with 
 trusses. The iron-work shall be so profwrtioned that the 
 weight of the structure, together with the above specified 
 rollmg load, shall in no part cause a tensile strain of more 
 than 10,000 lbs. per square inch of sectional area. Iron 
 used under tensile strain, shall be tough, ductile, of uniform 
 quality, and capable of sustaining not less than 50,000 lbs 
 per square inch of sectional area without fracture, and 
 25,000 lbs. per square inch without taking a permanent set. 
 The reduction of area at the breaking point shall average 
 25 per cent., and the elongation 15 j)er cent. When cold 
 the iron must bend, without sign of fracture, from 90 to 180 
 degrees." 
 
 A specification like the above, properl}- carried out, would 
 put an absolute stop to the building of puch structures as 
 the Tariffville bridge, and would prevent a very large part 
 of the catastrophies which so often shock the community, 
 and shake the public faith in iron bridges. We have 
 referred above to the factors of safety for wrought-iron 
 under tension only. Similar factors have been determined 
 for other kinds of materials, and for other kinds of strain. 
 
 15 
 
 The preceding remarks in regard to the loads for which 
 bridges should be designed, and the safe weight to be put 
 upon the material, are given to show how far the safety of a 
 given bridge is a matter of fact, and how far a matter of 
 opinion. It will be seen that the limits within which we are 
 at liberty to vary are quite narrow ; so that bridge-building 
 may correctly be caUed an exact science, and there is no ex- 
 cuse for the person who guesses either at the load which a 
 bridge should be deagued to bear or at the size of the dif- 
 ferent membei-s of the structure. Still less can we excuse 
 the man who not only guesses, but who, in order to build 
 cheaply, persistently guess on the wrong side. 
 
 We often hear it argued that a bridge must be safe since 
 it has been submitted to a heavy load and did not break 
 down. Such a test means absolutely nothing. It does not 
 even show that the bridge will bear the same load again; 
 much less does it show that it has the proper margin for 
 safety. It simply shows that it did not break down at that 
 time. Every rotten, worn-out and defective bridge that 
 ever fell has been submitted to exactly that test. More than 
 this, it has repeatedly happened that a heavy train has passed 
 over a bridge in apparent safety, while a much lighter one 
 passing directly afterward has gone directly through. In all 
 such cases the structure has been weak and defective, and 
 finally some heavy load i>asses over and cripples the bridge, 
 so that the next load produces a disaster. 
 
 It is very common upon the completion of a bridge to do 
 what is termed testing it. The common practice in England 
 is to load each track with as many engines and tenders as 
 the bridge will hold, and to measure the corresponding de- 
 flection. The proof-load varies from one and a half tons per 
 foot on the shorter bridges to one ton per foot upon longer 
 ones- but when the span exceeds 150 ft. in length the load is 
 made somewhat less. In France, the government rules for 
 testing wrought-iron railway bridges are as follows: Bridges 
 under 66 ft. span are loaded with a dead load of one and a 
 half tons per running foot, while bridges over 66 ft. span 
 are loaded with 1 i^ tons per foot. Besides the above proof, by 
 dead weight, a train composed of two engines, each with its 
 tender weighing at least 60 tons, and wagons each loaded 
 with 12 tons, in suflicient number to cover one span, are run 
 over the bridge at speeds from 12 to 22 miles an hour. A 
 second trial is made with speeds from 25 to 43 miles an 
 hour, with two engines, each with its tender weighing 35 
 
if 
 
 I !} 
 
 16 
 
 tons, and wagons as in ordinary passenger trains, enough to 
 cover one span. On double-track bridges two trains are 
 made to cross, at first in parallel and then in opposite di- 
 rections, so that the trains may meet at the centre. 
 
 Owing to the lack of any public supervision in the United 
 States, no general method for testing either railroad or 
 highway bridges exists. In some cases it is done, in some 
 cases it is not. Bridges made by our first-class firms, under 
 the direction of engineers, are tested in substantially the 
 same manner as in Europe; but upon many of our smaller 
 railroads, which cannot afford to keep an engineer, and 
 generally in the case of highway bridges, no test is made in 
 many instances for very obvious reasons. In one 
 case of wretchedly cheap and unsafe highway bridge 
 which came recently under the writer's notice, the county 
 commissioners, in order to quiet an impression which had 
 arisen that the bridge was not altogether sound, tested a 
 span 122 ft. long with a load estimated to weigh 58,600 lbs., 
 or 480 lbs. per running foot, for a double roadway. The com- 
 missioners remarked that they considered this a satisfactory 
 test, as it was not propable that a greater weight than thia 
 would ever be applied to the bridge ; and added that the test 
 was made merely to satisfy the public that the bridge was 
 abundantly safe for all practical uses. The public would, 
 no doubt, have been satisfied that the Ashtabula bridge 
 was abundantly safe for all practical uses had it stood on 
 that bridge in the morning and seen a heavy freight train 
 go over it ; and yet that very bridge broke down directly 
 afterwai-d under a passenger train. Now, according to the 
 common notion that was a good bridge in the morning, and 
 a very bad bridge, or rather no bridge at all, in the evening. 
 The question for the public is— When did it cease to be a 
 good bridge and begin to be a bad one i A test like the one 
 referred to above can do no more than illustrate the ignor- 
 ance or lack of honesty of those who make it, or those who 
 are satisfied with it. Such a test might come within a dozen 
 pounds of breaking the bridge down and no one would be 
 the wiser. 
 
 For the test of a bridge to be in any way satisfactory, we 
 must know just what effect such test has had upon the struc- 
 ture. We do not find this out by simply standing near and 
 noting that the bridge did not break down. We must, in 
 the first place, compute the strains which the load throws 
 upon ea«h pait of the bridge, and see that no member i» 
 
 17 
 
 over-strained. We must next measure precisely the amount 
 by which the bridge is depressed under the load, and also 
 how far the work recovers from such depression when the 
 load is removed. A locomotive, when first run on to a 
 bridge, will produce a certain depression— first, by the clos- 
 ing up and stretching of the joints, and sec- 
 ondly by the elongation and compression of 
 the material. If the load is left on for a considerable time 
 the depression wUl be seen to have slightly increased; but 
 after a longer time it will cease, the bridge having adapted 
 itself to the new conditions impresssd upon it. When the 
 load is removed, the work will recover its first position, less 
 a small amount, termed the permanent set. So long as the 
 load is kept within the proper limits this permanent set is 
 not increased by any number of subsequent applications of 
 the force that produced it, and no harm is done; but when 
 the load is so great that each application of the force in- 
 creases the set, we have passed the elastic limit, and failure 
 is only a question of time. It is important therefore to put the 
 load on a second time, and to be sure that the bridge does 
 not go below the point reached at first. In some cases a 
 second application of the load has appeared to increase the 
 permanent depression ; but it is quite likely that in such in- 
 stances the time during which the load was applied at first 
 was too short for the full effect to show itself. Ample time, 
 too, should be allowed for the material to recover after the 
 removal of the load. Mr. Stoney states that the set of 
 wrought-iron relaxes to a considerable extent, even after the 
 lapse of several days after the load has been removed. 
 
 In view of the preceding, what shall we say of a bridge 
 company that deliberately builds a bridge in the middle of a 
 large town, where it will be subjected to heavy teaming, and, 
 owing to its peculiar location, to heavy crowds, and war- 
 rants to the town that it shall hold a ton to the running foot, 
 when the very simplest computation shows beyond any 
 chance of dispute that such a load will strain the iron to 
 40,000 lbs. per square inch ? We are to say either that such 
 a company is so ignorant that it does not know the differ- 
 ence between a good bridge and a bad one, or else so wicked 
 as to knowingly subject the public to a wretchedly unsafe 
 
 bridge. 
 
 The case referred to is not an imaginary one, but exists 
 to-day in the main street of a large New England town. The 
 jointsinthatbridge which will safely hold but 20,000 lbs. 
 
T8 
 
 wiU be required to hold 60,000 Ibe. imder a load of one ton 
 per lineal foot, which the builders have warranted the 
 bridge to carry safely. The case was so bad that after a 
 lengthy controversy the town officers called a commission^ 
 and had a thorough expert examination of the bridge. The 
 commission reported as follows: first, *'The bridge in its 
 present condition might carry with tolerable safety the 
 ordinary daily traffic to which it is now subjected ;" second,. 
 " If a span of this bridge should at any time be subjected to 
 a closely packed mass of people on the draw-bridge, or a 
 loosely packed crowd on top of a heavy accumulation of 
 ice or snow, it would in either of these cases be in imminent 
 danger of falling, and would be so over-strained as to unfit 
 it for even moderate service;" thinj, "If the span should 
 have a heavy accumulation of ice or snow on it, and in that 
 condition be subjected to a close-packed mass of people, it 
 would certainly fall." The commission further reported 
 that the bridge at one place had a factor of safety of only 
 1 ,y^ ; and as this factor refers to the breaking weight, and 
 not to the elastic limit, the real factor would be about one- 
 half; or, in other words, half the load which is at any 
 time liable to come upon the bridge will strain it beyond 
 the elastic limit, while 1 Vrib times the load will break it 
 down. 
 
 Not\vitbstanding all this, and in the face of this report, 
 the president of the bridge company, came out with the 
 statement in the papers that he "pronounced the bridge per- 
 fectly safe." Thus we actuaUy have the president of a 
 bridge company in this country stating plainly that a factor 
 of It',5^, referred to the breaking weight, makes a bridge 
 " perfectly safe ;" for he very wisely made not the slightest 
 attempt to disprove any of the conclusions of the commission ; 
 and this company has built hundreds of highwav bridges all 
 over the United States, and is building them to-day where- 
 ever it can find town or county officers ignorant enough or 
 wicked enough to buy them. 
 
 It might be supposed that under the above condemnation 
 the authorities controlling the bridge would have taken 
 some steps to prevent the coming disaster. They did, how- 
 ever, nothing of the kind ; but allowed the public to travel 
 over it for more than a year, at the most fearful risk, until 
 public indignation became so strong that a special town- 
 meeting was called, and a committee appointed to remove 
 the old bridge and to build a new one. This is only one of 
 
 V 
 
 many cases just as bad which happen to be within the 
 writer's knowledge. 
 
 The Ashtabula bridge, it is stated in the Ohio report above 
 referred to, had factors — we can hardly call them factors of 
 safety— in some parts as low as 1 ^ and 1 ^q, such factors 
 referring to breaking weight ; and even these factors were ob- 
 tained by assuming the load as at rest, and making no allow- 
 ance for the jar and shock from a railway train in motion. 
 Well may the commissioners saj" as they do at the end of 
 their report : " The bridge was liable to go down at any 
 time during the last ten or eleven years, under the loads that 
 might at any time be brought upon it in the ordinary course 
 of the company's business, and it is most remarkable that it 
 did not sooner occur." 
 
 One point always brought forth when an iron bridge 
 breaks down, is the supposed deterioration of iron under re- 
 peated straining, and we are gravely told that after a while 
 all iron loses its fibre and becomes crystalline. This is one of 
 the ** mysteries " which some persons conjure up at tolerably 
 regular intervals to cover their ignorance. It is perfectly 
 well known by engineers the world over, that with good iron 
 properly used, nothing of the kind ever takes place. This 
 matter used to be a favorite bone of contention among engi- 
 neers, but it has long since been laid upon the shelf. 
 No engineer at the present day ever thinks of it. We 
 have only to allow the projjer margin for safety, as 
 our first-class builders all do, and this antiquated 
 obj?ction at once vanishes. The examples of the long dura- 
 tion of iron in large bridges are numerous and conclusive. 
 The Niagara Falls railroad suspension bridge was carefully 
 inspected after 22 years of continued use under frequent and 
 heavy trains, and not only was it impossible to detect by the 
 severest tests any deterioration of the wire in the cables, 
 but ft piece of it being thrown upon the floor curled up show- 
 ing the old " kink " which the iron had when made. The 
 Menai suspension bridge, in which 1,000 tons of iron have 
 hung suspended across an opening of nearly 600 ft. for 55 
 years, shows no depreciation that the most rigid inspection 
 could detect. Ii-on rods recently taken from an old wooden 
 bridge after 60 years of use have been carefully tested, and 
 found to have lost nothing either of the original breaking 
 strength or of the original elasticity. 
 
 The question is frequently asked, does not extreme cold 
 weaken iron bridges. To this it may be replied that no iron 
 
so 
 
 bridge made by a reliable company has ever shown the 
 slightest indication of any thing of the Idnd, though they 
 have been used for many years in Russia, Norway, Sweden 
 and Canada; and nothing that we know in regard to iron 
 gives us any reason to suppose that anything of the kind 
 ever will happen. But here again the whole question turns 
 npon the quality of the iron. Iron containing phosphorus is 
 •' cold short," or brittle, when cold, and will break quicker 
 under repeated and sudden shocks in cold weather than 
 when it is warm. It is a well-known fact that a good many 
 more rails break upon New England railroads in winter than 
 in sunmier. In Scandinavia this is not the case, simply be- 
 cause the iron used in that country is of the bpst quality. 
 In the words of Mr. Sandberg, the great Swedish authority 
 on iron, " Rails made of suitable iron with a proper section 
 will not break in winter. In Scandinavia, with a clhnate 
 more severe than in America, no accident has occurred from 
 broken rails. But a very small part of the rails shipped to 
 America \^'ill stand the proper test*. Iron highly impreg- 
 nated with phosphorus, or cold-short iron, is utterly unfit for 
 railroad purposes in countries subject to great and sudden 
 changes of temperature." An immense number of experi- 
 ments upon all sorts of iron show conclusively that cold has 
 no effect whatever upon the strength of good iron. The se- 
 curing such iron is a matter to which the utmost attention is 
 paid by our first-class bridge-building firms; but it is a mat- 
 ter to which no attention is paid by the builders of cheap 
 bridges. We might suppose that a person in putting an in 
 sufficient amount of iron into a bridge would be careful to 
 get the best quality; but exactly the reverse seems to be the 
 case; on the ground, perhaps, that the less of a bad thing we 
 have the better. 
 
 Many railroad companies in building wooden bridges take 
 no pains to get iron rods which are suitable for such work, 
 but purchase what is easiest to be had in the market, and in 
 many cases never find that the iron was bad until a bridge 
 tumbles down. There are,' without the slightest question, 
 hundreds of bridges now in use in this country, which as far 
 as mere proportions and dimensions go would appear to be 
 entirely safe, but which on account of the quality of the 
 iron with which they are made are entirely unsafe; and 
 there always will be as long as railway presidents, superin- 
 tendents or roadmasters buy iron which they know nothing 
 about, to put into bridges. When a bridge is finished the 
 
 81 
 
 ordinary examinations never detect the quality of the iron; 
 so that the wise remarks of many inspectors, or the opinions 
 of the ordinary hands employed on a road, as to the exact 
 condition of a bridge are of little or no value. 
 
 We often hear iron bridges condemned, while wooden 
 ones, so called, are supposed to be free from defects. It 
 does not seem to occur to persons holding such ideas that 
 wooden bridges rely just as much upon the strength of the 
 iron rods that tie the timbers together as upon the timber,, 
 and that the effect of cold is if anything worse upon the 
 iron rods in a wooden bridge than upon the rods in 
 an iron bridge, as in the latter all parts expand and 
 contract together, while in the former the rods 
 and the timbers are affected very differently. From 
 this cause it often happens that the rods in wooden 
 bridges in the northern part of the United States, where 
 the temperatnre varies from 30 degrees below zero to 90 
 above, by contracting bring upon themselves a strain enor- 
 mously greater than they were ever intended to bear. As a 
 matter of fact, where one iron bridge fails, a dozen wooden 
 ones do the same thing. One very decided advantage which 
 an iron bridge has over a wooden one is that we can make 
 sure of good iron in the beginning, and that we can also be 
 sure that it does not decay ; while, however good our timber 
 may be in the beginning, we can never be entirely sure of 
 its condition afterward. There are wooden bridges now 
 standing m this country all the way from 50 to 70 years old, 
 which are apparently as good as ever, while there ure others 
 not 10 years old which are so rotten as to be unfit for use. 
 Especially difficult is it to detect that most insidious foe to 
 timber, dry rot, which, lurking in the most inaccessible 
 places, often eludes the most faithful examination. It will 
 not do to assume that, because no defects are very evident in 
 a wooden bridge, therefore it has none. When a wooden 
 bridge, originally made of only fair material, has been 
 in use under railroad trains fol* S5 or 30 years, 
 and in a position where timber would naturally 
 decay, we are bound to suspect that bridge. To 
 assume such a bridge to be all right imtil we can prove 
 it to be all wrong, is not safe. To assume a bridge to be all 
 wrong until we can prove it to be all right is a safe method, 
 though not a popular one. Any person who has had oc- 
 casion to remove old wooden bridges will recall how often 
 they look very much worse than was anticipated. 
 
 r« 
 
fl-'f 
 
 btli 
 
 There is one defect in railway bridges which has often led 
 to the most fearful disasters, and which, without the slightest 
 question, can be almost entirely, if not entirely, removed, 
 and at a moderate cost. At least half the most disastrous 
 failures of railroad bridges in the United States have been 
 due to a defective system of flooring. With a very laige 
 number of our bridges the failure of a rail, the breaking of 
 an axle, or anything which shall throw the train from the 
 track, is almost sure to be followed by the breaking down of 
 the bridge. This was without question the cause of the re- 
 cent disaster at St. Charles. A truck near the middle of a 
 train of 17 loaded stock cars broke down, so that the car left 
 the track, cut through the floor, destroyed the lat<rral brac- 
 ing and dragged the trusses down on top of it. With the ex- 
 ception of the floor this was one of the finest bridges in the 
 United States, and was built by one of our very best bridge- 
 building firms. This was one of four railway bridges 
 destroyed from the same cause, derailment, in the single 
 month of November last. The report of the American 
 Society of Civil Engineers referred to on a preceding page 
 observes in regard to this matter : 
 
 " In most of our railroad bridges the floor system is the 
 weak ix)int. The cross-ties are short, the stringers are pro- 
 portioned for a train on and not off the rails, and the guard 
 timbers are too low and insufliciently bolted. A derailed en- 
 gine on such a floor as this plunges CS the ends of the cross- 
 ties, into the open space between the stringers and the chords, 
 and generally wrecks the bridge. To ob^te this, all cross- 
 ties should extend from truss to truss, and be placwl so close 
 to each other that, if sui)ported at the proper intervals it 
 will be impossible for a derailed engine to cut through them; 
 and the stiingers should be so spaced as to give them this 
 support. Next, the guard timbers should not be less than 
 9x10 inches, and should be strongly bolted or spiked to each 
 alternate cross- tie; and lastly, the clear width between the 
 trusses should be so great that the wheels of a deraile<l train 
 will be arrested by the guard rail before the side of the wid- 
 est car can strike the truss. " 
 
 Another point, which has often been neglected is making 
 sufficient i)rovision to resist the force of the wind. A tornado 
 such as is not uncommon in this countr>', will exert a force 
 of 40 lbs. per square foot, which upon the side of a wooden 
 bridge, say of 900 ft. span and 25 ft. high, and boarded up 
 as many bridges are, would amount to a lateral thrust of no 
 jess than 100 tons; and this weight would be applied in the 
 worst possible manner, i. «•., in a series of shocks. There 
 have been many cases in this country where bridges have 
 
 \ 
 
 28 
 
 4)een blown down, and a case recently came to the writer's 
 notice where an iron railroad bridge of 180 ft span and 30 
 ft. high, of the Whipple pattern, and presenting apparently 
 almost no surface to the wind, was blown so much out of 
 line that the track ha<? to be moved. No doubt the recent 
 terrible disaster at the Frith of Tay was due to this cause. 
 
 At the time of the Tariflfville catastrophe it was gravely 
 stated at the coroner's inquest, and by railroad officers who 
 claimed to know about such things, that the disaster was 
 caused by the tremendous weight of two locomotives which 
 were coupled together, and it was stated that one engine 
 would have passed in safety; and directly afterward the 
 superintendent of a prominent railroad in New England is- 
 sued an order forbidding two engines connected to pass 
 over any iron bridges. It is all very well for a company to 
 issue such an order so far as it may give the public to under- 
 stand that it is determined to use every precaution 
 Against disaster, but such an order may have the effect of 
 <;i-eating a distrust which really ought not to exist. If a rail 
 road bridge is not entirely safe for two engines, it is certain- 
 ly entirely unsafe for one engine and the train following, 
 the only saving in weight by taking off one engine being the 
 difference lietween the weight of that engine and the weight 
 of the cars that would occupy the same room. For example, 
 a bridge of 200 ft. span will weigh 1,500 lbs. per lineal foot. 
 An engine with its tender will weigh 60 tons in a length of 
 60 ft., and a loaded freight train may easily weigh two- 
 thirds of a ton per lineal foot. The total weight of the span, 
 with two engines and the rest of the bridge covered with 
 loaded freight cars, would therefore be 320 tons. If we 
 take off one engine and fill its place with cars, we take off 
 60 tons and put in its place 33 tons; ». e., we remove 27 tons, 
 or just about one-twelfth of the working hmd. Taking off a 
 large part of the working load, however, is taking off a very 
 small part of the breaking load. With a factor of safety of 
 six, for example, taking off one-twelfth of the working load 
 is taking off less than one-seventieth of the breaking load. 
 An order, therefore, like that above can only be of use when 
 fhe working load and the breaking load are so near alike 
 that the actual load is a dangerous one ; that is, when the 
 bridge is unfit for any traffic whatever; so that if such an 
 order was reaUy needed, it would in itself be in the eyes of 
 an engineer a condemnation of the bridge. 
 Having seen something of the structures which require in- 
 
 
\ 
 
 
 r-j. 
 
 t 
 
 specting, let us now see whnf ti^^ ^# • 
 
 this country, and thrriS^l '^fi "'^nT'"" ? """ '" 
 inspection which we m.Vhf h! ^ let u» uJk, see the 
 
 be produced 2>o4Tfl^t ^^^7^^" "^"^ "»' "^"t 
 suppled that n^Sd^so^Sr^ ^T"' • "* 
 such structures in good orrlAr "'"'""'"*'«<*« in Iceeping 
 those bridges, and ll^t^Z Z SLT**'"" ""'"' ""■' 
 «*er. This is of .v,,/.! u *" ""^ '" "»«« »' ("is- 
 
 over half anUllion doZ^N^ittdTT"^ """'"""« 
 down which the owners wL "° ™''^'«<» ''"'•ge ever broke 
 
 but there is^^:^^TZZtTT^'"'"^'"''^'^''' 
 Penses unU, the Lt moZnt, auTthl S'* '"^'' "'" 
 
 a ie^siativf — SI •tTnrr o/'l^ ^^^ 
 roads were not safe tn .T ^°'*^^®'* 
 
 such roads w.>r«Ko- . '^"^ ^^^'■' but that 
 
 keep ^i^ ;^t Z^ " ^'■™«- r ™""' "•" '"'°"' to 
 the past ten 7«r."ter?Xi;!^??.r '"'"'"■ ^•^'^ 
 States have broken dowl t^ ^"^ ''"'^ *» the United 
 
 suchinspectionLthtmUnl ''""^"^"■'"'^P'""''" 
 
 the supervision t^dXtiveofth?" "^"""^ ''"*"'^«' 
 continued the use of ^XZZ^tT^::.TT<''y 
 means been confined f^ thJ ^ '*"^^ ***« ^X »<> 
 
 would seem,reX^t.lT .Wwr^nr "^"^ '* 
 themselves has not bee; suffleienT^u^^^„^t ~""*''**» 
 enough t» prevent ion T ! " '*tau''y has not been 
 
 cust^^inse^eXU^U^'^^sl^Lf""*^- "" "« 
 termed a railroad comm,L"r^ ?^. T""*"" '"»' '» 
 
 to have been for f ^ ^^ "^"'' '"tention seems 
 
 under som^ld"fX«r^°" "^ """• ^^^ "•"-<». 
 settling the vario^ C"s' rhlL" Z LT- *" ^^^ *" 
 different railroad companir I„H . 7* " '*'"**° 
 
 paniesandthepub^ uZ'theUt. °*° railroad com 
 quickly dismiss' a^\u^J, Jft "Z** "^'^ '^^. """^ 
 organi^tions. It is Ir.^/ uT^VX^^'Z^^Zr 
 
 ^h^TLs^lTtbT •*""'' ""■ ""«»« 
 
 questions " 'a Z^^Z "Z i"*^,*"" «»^««f1 
 Pointees. Even in'trcTusett'^whrro ?^e'"*', '^ 
 commission app^„ini,, best aspect. rtt':i^tUtTtf 
 
 25 
 
 strongest advocates, after ten years of existence, to be but 
 ■an experiment which cannot yet be pronounced an assured 
 success. With regard to the value of the inspection of 
 bridges, by any such commissions, we should hardly suppose 
 that three men, in many cases entirely unacquainted with 
 mechanical matters, could by riding over a railroad once or 
 twice a year, occasionally getting out to examine the paint 
 on the outside of the boards which conceal a truss from 
 view, judge very correctly of the elastic limit of the iron 
 which they have never seen, and of which they do not even 
 know the existence. 
 
 For ample proof of the utter inefficiency of the present 
 system of public inspection, we have only to compare the 
 reports of the railroad commissioners in almost any state 
 with the actual condition of the structures described. The 
 writer has done this to a certain extent in several states, in 
 which he has now a personal knowledge of many bridges. In 
 one state the last annual report covers a whole railroad witE 
 the remark, " All of the bridges on this line are in excellent 
 order ; " and yet there were at that very time, and ai-e now, on 
 that road, several large wooden bridges with a factor of safety, 
 referred to the breaking weight, of not over two, under a fair 
 load, assuming the iron rods to be of the very best material, a 
 point upon which the'-e is no evidence whatever. In another 
 state an iron bridge is in use under heavy trains which has a 
 factor of only two and a half, and yet the state report pro- 
 nounces it an excellent structure and a credit to the railroad 
 company (which furnished the commission with free passes). 
 In a third case the commissioners stated plainly to the writer 
 that a certain bridge was undoubtedly weak, but that it was 
 on a line over which very few passengers traveled. A man's 
 neck, however, is as valuable, as far as the owner is con- 
 cerned, oti one road as on another. In one instance, in an- 
 swer to the enquiry how the coromiFsioners had been able to 
 report upon a large wooden bridge, which was so covered 
 in as to be entirely hidden, it was replied : '• Well, we went 
 over that bridge in the night ; but the road-master told us 
 that the bridge was in good order." No wonder that rail- 
 road officials have an undisguised contempt for the state in- 
 spection. The commissioners of three of the most import- 
 ant states in the Union did not hesitate to admit to the writ- 
 er a year ago that no one of them had ever computed the 
 strains on a single bridge in the state, but supposed that to 
 be the business of the builder ; and one ofiicer, in reply to a 
 
 i) 
 
 iMnMll 
 
 
\ 
 
 ■such in^peotion^tLt irr "retlSr"^ r^htrr'^ 
 T^iffvnie bridges, fe„ and kuJS^veTir^t e "^ 
 
 WhUe m a ew »tate, the inspection is not^r^. bad .. 
 
 bHdg^dJi:';^,r;r,»^r:''"™"'*'"'^"^'"«»'^«> 
 
 -o^'tiJ'C !: lif '""^ ''"'^' "« ■«• « Po-iWe, even 
 
 be less than 800. This is about nn '^''°* 
 
 every two states, and is no d:ubt J^withT: th' IZ. '7, 
 
 bnd.e-bui.aerrthr^„r.,*:„rsr" '•^- '"^-- 
 
 gard to bridges or bridge-builders In J3? . "" "^ 
 from some one conveiSit «-^h '°^^«» of gettmgadvice 
 
 themselves to belm^ l" „ k .k "'"*'*'''' *"">' »"°»«^ 
 
 they knewnotWngaC^ Tbn^d^" '*^"' "' * '*°«'"' 
 
 to make its own tcwlioI'^.^T.irTthTL^Z:' 
 
 ^oLrr;::rar::-':-rTr^^^ 
 
 t 
 
 87 
 
 price, and gave the town a bridge which a committee of 
 experts reportetl had a factor of safety of 1 15-lOOths, and 
 would cei-tainl y fall under a heavy load. Add to this the 
 fact that the county com nissioners iu the next town, in full 
 knowledge of all that had been done above, deliberately pro- 
 ceeded to employ the same company to make another bridge of 
 exactly the same kind, and we can see pretty clearly the value 
 of the present system, if it can be called such, of highway 
 bridge work in this coimtry ; and the above is a perfectly 
 fair specimen of the general practice in the United States. 
 
 If we knew positively that in just six months a terrible 
 disaster would occur under the present system of railroad 
 inspection, and knew also that by a better system such dis- 
 aster would certainly be prevented, it is possible that a 
 change would be made. We know that a proper method of 
 building and of inspecting bridges would certainly have pre- 
 vented the disasters at Ashtabula, Tariff ville and Dixon. 
 We know that the inspection which those bridges received ^ 
 did not prevent three of the most fearful disasters the 
 country has ever seen. Admitting, now, that structures so 
 important to the public safety as bridges both upon roads 
 and railroads ought to be kept under rigid inspection and 
 control, and that no system at present existing has been able 
 to prevent the most fearful catastrophes, what shall we do ? 
 Directly after the Ashtabula disaster the Ohio legislative 
 committee appointed to investigate that affair presented a 
 bill, evidently suggested by the report of the American So- 
 ciety of Engineers, '*To secure greater safety for public 
 travel over bridges," in which was plainly specified the 
 loads for which all bridges should be proportioned, 
 the maximum strains to which iron should be subjected, 
 and a method for inspecting the plans of all bridges before 
 building and the bridges themselves during and after con 
 struction. The Governor, with the consent of the Senate, 
 was to appoint the inspector for a term of five years, at a 
 salary not exceeding $3,000 a year; such inspector to pass 
 a satisfactory examination before a Ck>mmittee of the 
 American Society of Engineers, themselves practical experts 
 in bridge construction, and he was also to take a suitable 
 •oath for the faithful performance of his duty. This bill 
 never became a law. An appropriation was made for a 
 short time to pay for certain examinations, and there the 
 matter stopped. 
 
 The Committee of the American Society of Engineers 
 
28 
 
 were not agreed upon this matter. Messrs James R 
 f:^J:'t2T. "*^-^^«-^*»^-«^tedthe^p;^„Tm\n,' 
 
 e^'^^'havet:" "" "^'^ ^*^^"^^ "^ inspected, "ct 
 expert to have been examined and approv^ bv thl 
 
 Amencan Society of Engineers. This insp^^ ^^ ^L'^ 
 
 vi^t the scene of every accident, so cai^^^d Toas^^ 
 
 as far as possible the cause. Messrs. Thomas C Cl^^ 
 
 that i/^' . ^^ °'^**'^ ^^^^ ^ impracticable, and fWed 
 that ,f mspectors were appointed, it wouJd be by polkic^ 
 fluence, and that the result would be worse than at'^^T t 
 
 ISmv"""^ incaaeoradtaaster io^tZryZ^ 
 
 paK»f, snouid be the legal standard, and in case ii- «h«»w i^ 
 ^u^d that aay bridge „aa o, !«. ^ngthlbrt^ t "ho„i^ 
 be taken as pnma /aw evidence of neglect on the n-H^f 
 
 ^^ .h.tL .Cfr3"Lrxr;nrtre3rjrtt 
 
 corporation having control o( it had been deDcitJT with ,k 
 American Society, and further, that^^pri^'^p":!'^? 
 
 Tke^^W "„?*''"'";"' •« "tamped With' t^e^'^^rthi 
 maker, ptace of manufacture and date. Messrs Alfred P 
 
 it tL' H '"^"" *^""»'"' '*"'«• "'therTwa^^ect: 
 Wfa^ tt"::? "T"'- '"' ™'»«<^«-<f public sentimen^y 
 
 »re to keep the number of .ppHca^rdorntat-S 
 low figure. In case such a plan was found fearibirk^th! 
 
 ^etS^n e21 '"T- "^ "'~" "■" -^«i"n''of 
 Me oociety of Engineers, as inspector of roads and bridirea 
 or state engineer. Pay him for his whole time and iTt 7^' 
 give his whole time to the work, for he wiUnt^STdo ^ 
 '»uch person should have in his i««ession a co^let^ «? oi 
 
 \ 
 
 29 
 
 plans of every bridge of importance in the state, with ail 
 the computations of its strength, and as complete a history 
 of each structure from its commencement as can ixjssibly 
 be made up, all this to be supplemented by at least tw© annual 
 examinations. If from such records we find that a bridge 
 was made of ordinary green timber, 25 years ago, and that 
 it has been getting rotten ever since, that it has rods of com- 
 mon merchant-iron that were bought by the president or 
 superintendent of a railroad from an unknown firm, we 
 had better pull it down before it falls. If from such records 
 we find an iron bridge, built 25 years since by an unknown 
 company, with iron at best of doubtful quality, and having 
 a factor of three or four for the rolling-stock and speeds of 
 twenty years ago, instead of a factor of six for the rolling- 
 stock and speeds of to-day, we had better remove that bridge 
 before it removes itself. 
 
 Such a record would be the property of the state, always 
 accessible to any oqe, and would be handed down, so that 
 the knowledge of one person would not expire with his term 
 of oflBce. No bridge should be erected in any state, with- 
 out first submitting the plans to the inspector, and receiving 
 his approval, and depositing with him a complete set of the 
 plans and computations for the work. By this approval, is 
 not meant that the inspector is merely to give a favorable 
 opinion as to the plan, but that he is to find, as a matter of 
 fact, whether the proposed dimensions and proportions are 
 such as will make a safe bridge; and just what a safe bridge 
 is can be plainly defined by law, as it is in Europe, and as it 
 has been proposed by the American Society of Civil Engi- 
 neers. ^ For example, if the law says that an iron railway 
 bridge of 100 feet span shall be proportioned to carry a loaa 
 of 3,000 lbs. per lineal foot, besides its own weight; and that 
 with such a load no part shall be strained by more than 10,- 
 000 ibs. per inch; all the inspector has to do is to go over the 
 figures and see if the given dimensions on the plan are such 
 as will enable the bridge to cany the load without exceeding 
 the specified strains. When the work is erected, the inspec- 
 tion must know that the plan has been exactly carried out, 
 and good evidence of the quality of the material used should 
 also be given. Such inspection as this would at once 
 prevent the erection of bridges like those at Ashtabula and 
 Tariflfville, and would save the public from such traps as 
 that at Dixon, and the one at)ove referred to as having a 
 factor of safety of l^^o 
 
80 
 
 or eont.0. .t p^„t exiSnX b^^ S^" ^JtTtT 
 van^ the defect in the«, ,tr„ctu„«. or to p^^rthe i^" 
 
 ne tad, which If properly carried out will insure in nearir 
 
 ac Z:; wh"!"^'- "^ -•"•"<= »""^- » «« with theT^ 
 Uc to say whether or not it will have such a system. 
 
 \ 
 
tl'"'^''' 
 
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 Bridge disasters in Amerioa: the 
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