,,bridge ,,disasters ,,in ,,america ,the ,cause and the ,remedy ,,by ,,george ,l4 ,,vose ,,author ,,of ,,manual ,,for ,,railroad ,,engineers ,,and ,,engineering ,,students1 ,,life ,,and ,,works ,,of ,,george ,w4 ,,whistler1 ,,civil ,,engineer1 ,,etc4 ,,eternal ,,vigilance ,,is ,,the ,,price ,,of ,,liberty ,,boston ,,lee ,,and ,,shepard ,,publishers #aj ,,milk ,,street ,,next ,,old ,,south ,,meeting ,,house #ahhg ,,note4 ,the substance of the following pages appeared originally in ,the ,railroad ,gazette4 ,it was afterwards reproduced in pamphlet form1 and has since been several times delivered as an address to various bodies1 the last occasion being before the ,legislature of ,massachusetts1 #ahhg4 ,it is now re-published1 with some new matter added1 in the hope that the public attention may be called to a subject which has so important a bearing upon the public safety4 ,,copyright1 #ahhg1 ,,by ,,lee ,,and ,,shepard4 ,all rights reserved4 ,,bridge ,,disasters ,,in ,,america4 ,nearly all of the disasters which occur from the breaking down of bridges are caused by defects which would be easily detected by an efficient system of inspection4 ,not less than forty bridges fall in the ,united ,states every year4 ,no system of public inspection or control at present existing has been able to detect in advance the defects in these structures1 or to prevent the disasters4 ,after a defective bridge falls1 it is in nearly every case easy to see why it did so4 ,it would be just about as easy1 in most cases1 to tell in advance that such a structure would fall if it ever happened to be heavily loaded4 ,hundreds of bridges are to-day standing in this country simply because they never happen to have received the load which is at any time liable to come upon them4 ,a few years ago an iron highway bridge at ,dixon1 ,ill41 fell1 while a crowd was upon it1 and killed sixty persons4 ,the briefest inspection of that bridge by any competent engineer would have been sure to condemn it4 ,a few years later the ,ashtabula bridge upon the ,lake ,shore ,railroad broke down under an express train1 and killed over eighty passengers4 ,the report of the committee of the ,ohio ,legislature appointed to investigate that disaster concluded1 first1 that the bridge went down under an ordinary load by reason of defects in its original construction2 and1 secondly1 that the defects in the original construction of the bridge could have been discovered at any time after its erection by careful examination4 ,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 characterize so much of the management of the public works in this country4 ,there are many bridges now in use upon our railroads in no way better than those at ,ashtabula and ,tariffville1 and which await only the right combination of circumstances to tumble down4 ,there are1 by the laws of chance1 just so many persons who are going to be killed on those bridges4 ,there are hundreds of highway bridges now in daily use which are in no way safer than the bridge at ,dixon was1 and which would certainly be condemned by five minutes of competent and honest inspection4 ,more than that1 many of them have already been condemned as unfit for public use1 but yet are allowed to remain1 and invite the disaster which is sure to come4 ,can nothing be done to prevent this reckless and wicked waste of human life8 ,can we not have some system of public control of public works which shall secure the public safety8 ,the answer to this question will be1 ,not until the public is a good deal more enlightened upon these matters than it is now4 ,it has been very correctly remarked1 that1 in order to bring a disaster to the public notice1 it must be emphasized by loss of life4 ,the ,ashtabula bridge fell1 and killed over eighty persons2 and a storm of indignation swept over the country1 from one end to the other4 ,no language was severe enough to apply to the managers of the ,lake ,shore ,railroad2 but if that very bridge had fallen under a freight-train1 and no one had been injured1 the occurrence would have been dismissed with a paragraph1 if1 indeed1 it had received even that recognition4 ,in ,february1 #ahgi1 a span one hundred and ten feet long of an iron bridge on the ,chicago and ,alton ,railroad at ,wilmington fell as a train of empty coal-cars was passing over it1 and three cars were precipitated into the river1 a distance of over thirty feet4 ,no one was injured4 ,not a word of comment was ever made in regard to this occurrence4 ,suppose1 that1 in place of empty coal-cars1 the train had consisted of loaded passenger-cars1 and that one hundred persons had been killed4 ,we know very well what the result would have been4 ,is not the company just as much to blame in one case as the other8 ,on the night of the #hth of ,november1 #ahgi1 one span of the large bridge over the ,missouri at ,st4 ,charles gave way as a freight-train was crossing it1 and seventeen loaded stock-cars fell a distance of eighty feet into the river4 ,two brakemen and two drovers were killed4 ,this bridge1 says the only account that appeared in the papers1 did not break apparently1 for the whole span went down with the cars upon it4 ,it could hardly make much difference to the four men who were killed1 whether the bridge broke down1 or went down4 ,not a word of comment was ever made in the papers outside of ,missouri in regard to this disaster4 ,suppose1 that1 in place of seventeen stock-cars1 half a dozen passenger-cars had fallen from a height of eighty feet into the river1 and that1 in place of killing two brakemen and two drovers1 two or three hundred passengers had been killed4 ,is not the public just as much concerned in one case as in the other8 ,suppose that a bridge now standing is exactly as unsafe as the ,ashtabula bridge was the day before it fell1 would it be possible to awaken public attention enough to have it examined8 ,probably not4 ,about two years ago an attempt was made to induce one of the leading dailies in this country to expose a wretchedly unsafe bridge in ,new ,england4 ,the editor declined1 on the ground that the matter was not of sufficient interest for his readers2 but less than a month afterwards he devoted three columns of his paper to a detailed account of a bridge disaster in ,scotland1 and asked why it was that such things must happen1 and if there was no way of determining in advance whether a bridge was safe1 or not8 ,this editor certainly would not maintain1 that1 in itself1 it was more important to describe a disaster after it had occurred than to endeavor to prevent the occurrence2 but1 as a business man1 he knew perfectly well that his patrons would read an account giving all of the sickening detail of a terrible catastrophe1 while few1 if any1 would wade through a dry discussion of the means for protecting the public from just such disasters4 ,the public is always very indignant with the effect1 but does not care to trouble itself with the cause2 but the effect never will be prevented until the cause is controlled2 and the sooner the public understands that the cause is in its own hands1 to be controlled1 or not1 as it chooses1 the sooner we shall have a remedy for the fearful disasters which are altogether too common in the ,united ,states4 ,in a country where government controls all matters on which the public safety depends1 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 authority1 where no work can be executed except under the rigid inspection of the best experts1 nor opened to the public until it has been officially tested and accepted1 it makes little or no difference whether the public is informed1 or not1 upon these matters2 but in a country like the ,united ,states1 where any man may at any time open a shop for the manufacture of bridges1 whether he knows any thing about the business1 or not1 and is at liberty to use cheap and insufficient material1 and where public officers are always to be found ready to buy such bridges1 simply because the first cost is low1 and to place them in the public ways1 it makes a good deal of difference4 ,there is at present in this country absolutely no law1 no control1 no inspection1 which can prevent the building and the use of unsafe bridges2 and there never will be until the people who make the laws see the need of such control4 ,there is no one thing more important in this matter than that we should be able to fix precisely the blame in case of disaster upon some person to whom the proper punishment may be applied4 ,if every railway director1 or town or county officer1 knew that he was held personally accountable for the failure of any bridge in his charge1 we should soon have a decided improvement in these structures4 ,if we could show that a certain bridge in a large town had been for a long time old1 rotten1 worn out1 and liable at any moment to tumble down1 and could show in addition1 that the public officers having charge of such a bridge knew this to be the case1 and still allowed the public to pass over it1 we can see at once1 that1 in case of disaster1 the blame would be clearly located1 and the action for damages would be short and decisive4 ,once let a town have heavy damages to pay1 and let it know at the same time that the town officers are clearly accountable for the loss1 and it is possible that it would be willing to adopt some system that should prevent the recurrence of such an outlay4 ,to see what may be accomplished by an efficient system of public inspection1 it is necessary to know something in regard to the structures to be inspected4 ,we have now in common use in this country1 both upon our roads and our railroads1 bridges made entirely of iron1 bridges of wood and iron combined1 and occasionally1 though not often nowadays1 a bridge entirely of wood2 and these structures are to be seen of a great variety of patterns1 of all sizes1 and in every stage of preservation4 ,of late so great has been the demand for bridge-work1 that this branch of engineering has become a trade by itself2 and we find immense works fitted up with an endless variety of the most admirably adapted machine-tools devoted exclusively to the making of bridges of wood1 iron1 steel1 or all combined4 ,as in all division of labor1 the result of this specialization has been to improve the quality of the product1 to lessen the cost1 and to increase the demand1 until many of our large firms reckon the length of bridging which they have erected by miles instead of feet4 ,as usual1 however1 in such cases1 unprincipled adventurers are not wanting1 who1 taking advantage of a great demand1 do not hesitate to fit up cheap shops1 to buy poor material1 and to flood the market with a class of bridges made with a single object in view1 viz41 to sell1 relying upon the ignorance--or something worse--of public officials for custom4 ,not a year passes in which some of these wretched traps do not tumble down1 and cause a greater or less loss of life1 and at the same time1 with uninformed people1 throw discredit on the whole modern system of bridge-building4 ,this evil affects particularly highway bridges4 ,the ordinary county commissioner or selectman considers himself amply competent to contract for a bridge of wood or iron1 though he may never have given a single day of thought to the matter before his appointment to office4 ,the result is1 that we see all over the country a great number of highway bridges which have been sold by dishonest builders to ignorant officials1 and which are on the eve of falling1 and await only an extra large crowd of people1 a company of soldiers1 a procession1 or something of the sort1 to break down4 ,not many years ago1 a new highway bridge of iron was to be made over one of the principal rivers in ,new ,england4 ,the county commissioners desired a well-known engineer1 especially noted as a bridge-builder1 to superintend the work1 in order to see that it was properly executed4 ,the engineer1 after inspection of the plans1 told the commissioners plainly that the design was defective1 and would not make a safe bridge2 and that1 unless it was materially changed1 he would have nothing to do with it4 ,the bridge1 however1 was a cheap one1 and1 as such1 commended itself to the commissioners1 who proceeded to have it erected according to the original plan2 and these same commissioners now point to that bridge1 which has not yet fallen1 but which is liable to do so at any time1 as a complete vindication of their judgment1 so called1 as opposed to that of the engineer who had spent his life in building bridges4 ,an impression exists in the minds of many persons1 that it is purely a matter of opinion whether a bridge is safe1 or not4 ,in very many cases1 however1--perhaps in most1--it is not at all a matter of opinion1 but a matter of fact and of arithmetic4 ,the whole question always comes to this3 ,is the material in this bridge of good quality8 ,is there enough of it8 ,is it correctly disposed1 and properly put together8 ,with given dimensions1 and knowing the load to be carried1 it is a matter of the very simplest computation to fix the size of each member4 ,we know what one square inch of iron will hold1 and we know1 also1 the total number of pounds to be sustained2 and it is no matter of opinion1 but one of simple division1 how many times one will go into the other4 ,but it may be asked1 ,can the precise load which is coming upon any structure be exactly fixed8 are not the circumstances under which bridges are loaded very different8 ,bridges in different localities are certainly subjected to very different loads1 and under very different conditions2 but the proper loads to be provided for have been fixed by the best authority for all cases within narrow enough limits for all practical purposes4 ,few persons are aware of the weight of a closely packed crowd of people4 ,mr4 ,stoney of ,dublin1 one of the best authorities1 packed #cj persons upon an area of a little less than #cj square feet2 and at another time he placed #eh persons upon an area of #eg square feet1 the resulting load in the two cases being very nearly #aej pounds to the square foot4 ,such cramming1 says ,mr4 ,stoney1 could scarcely occur in practice1 except in portions of a strongly excited crowd2 but ,i have no doubt that it does occasionally so occur4 ,in my own practice1 he continues1 ,i adopt #ajj pounds per square foot as the standard working-load distributed uniformly over the whole surface of a public bridge1 and #adj pounds per square foot for certain portions of the structure1 such1 for example1 as the foot-paths of a bridge crossing a navigable river in a city1 which are liable to be severely tried by an excited crowd during a boat-race1 or some similar occasion4 ,tredgold and ,rankine estimate the weight of a dense crowd at #abj pounds per square foot4 ,mr4 ,brunel used #ajj pounds in his calculations for the ,hungerford ,suspension ,bridge4 ,mr4 ,drewry1 an old but excellent authority1 observes that any body of men marching in step at from #c to #c-a_/b miles an hour will strain a bridge at least as much as double the same weight at rest2 and he adds1 ,in prudence1 not more than one-sixth the number of infantry that would fill a bridge should be permitted to march over it in step4 ,mr4 ,roebling says1 in speaking of the ,niagara ,falls ,suspension ,bridge1 ,in my opinion1 a heavy train1 running at a speed of #bj miles an hour1 does less injury to the structure than is caused by #bj heavy cattle under full trot4 ,public processions marching to the sound of music1 or bodies of soldiers keeping regular step1 will produce a still more injurious effect4 ,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 district4 ,a bridge that is strong enough is just as good and just as safe as one that is ten times stronger1 and even better2 for in a large bridge1 if we make it too strong1 we make it at the same time too heavy4 ,the weight of the structure itself has to be sustained1 and this part of the load is a perpetual drag on the material4 ,in #ahge the ,american ,society of ,civil ,engineers1 in view of the repeated bridge disasters in this country1 appointed a committee to report upon ,the ,means of ,averting ,bridge ,accidents4 ,we might expect1 when a society composed of some hundreds of our best engineers selects an expert committee of half a dozen men1 that the best authority would be pretty well represented2 and such was eminently the case4 ,it would be impossible to have combined a greater amount of acknowledged talent1 both theoretical and practical1 with a wider and more valuable experience than this committee possessed4 ,the first point taken up in the report is the determination of the loads for which both railroad and highway bridges should be proportioned4 ,in regard to highway bridges1 a majority of the committee reported that for such structures the standard loads should not be less than as shown in the following table3-- ---------------------------------------- --------- ,,pounds ,,per ,,square ,,foot4 ,,span4 ------------------------------ ,,class ,a4 ,,class ,b4 ,,class ,c4 ---------------------------------------- --------- #fj feet and less #ajj #ajj #gj #fj to #ajj feet #ij #ge #fj #ajj to #bjj feet #ge #fj #ej #bjj to #djj feet #fj #ej #dj ---------------------------------------- --------- ,class ,a includes city and suburban bridges1 and those over large rivers1 where great concentration of weight is possible4 ,class ,b denotes highway bridges in manufacturing districts having well-ballasted roads4 ,class ,c refers to ordinary country-road bridges1 where travel is less frequent and lighter4 ,a minority of the committee modified the table above by making the loads a little larger4 ,the whole committee agreed in making the load per square foot less as the span is greater1 which is1 of course1 correct4 ,it would seem eminently proper to make a difference between a bridge which carries the continuous and heavy traffic of a large city1 and one which is subjected only to the comparatively light and infrequent traffic of a country road4 ,at the same time it should not be forgotten1 that1 in a large part of the ,united ,states1 a bridge may be loaded by ten1 fifteen1 or even twenty pounds per square foot by snow and ice alone1 and that the very bridges which from their location we should be apt to make the lightest1 are those which would be most likely to be neglected1 and not relieved from a heavy accumulation of snow4 ,in view of the above1 and remembering that a moving load produces a much greater strain upon a bridge than one which is at rest1 we may be sure1 that1 as the committee above referred to recommend1 the loads should not be less than those given in the table4 ,we can easily see that in special cases they should be more4 ,there is another point in regard to loading a highway bridge1 which is to be considered4 ,it often happens that a very heavy load is carried over such bridges upon a single truck1 thus throwing a heavy and concentrated load upon each point as it passes4 ,mr4 ,stoney states that a wagon with a crank-shaft of the ,british ship ,hercules1 weighing about forty-five tons1 was refused a passage over ,westminster iron bridge1 for fear of damage to the structure1 and had to be carried over ,waterloo bridge1 which is of stone2 and he says that in many cases large boilers1 heavy forgings1 or castings reach as high as twelve tons upon a single wheel4 ,the report of the ,american ,society of ,civil ,engineers1 above referred to1 advises that the floor system be strong enough to carry the following loads upon four wheels3 ,class ,a1 #bd tons2 ,class ,b1 #af tons2 ,class ,c1 #h tons2 though it is stated that these do not include the extraordinary loads sometimes taken over highways4 ,this provision for local loads1 says ,mr4 ,boller1 one of the committee1 may seem extreme2 but the jar and jolt of heavy1 spring-less loads come directly on all parts of the flooring at successive intervals1 and admonish us that any errors should be on the safe side4 ,to pass now to railroad bridges1 we find here a very heavy load coming upon the structure in a sudden1 and often very violent1 manner4 ,experiment and observation both indicate that a rapidly moving load produces an effect equal to double the same load at rest4 ,this effect is seen much more upon short bridges1 where the moving load is large in proportion to the weight of the bridge1 than upon long spans1 where the weight of the bridge itself is considerable4 ,the actual load upon a short bridge is also more per foot than upon a long one1 because the locomotive1 which is much heavier than an equal length of cars1 may cover the whole of a short span1 but only a part of a longer one4 ,the largest engines in use upon our railroads weigh from #ge1jjj to #hj1jjj pounds on a wheel-base of not over twelve feet in length1 or #b1hjj pounds per foot for the whole length of the engine1 and from #bj1jjj to #bd1jjj pounds on a single pair of wheels4 ,the heaviest coal-trains will weigh nearly a ton to the foot1 ordinary freight-trains from #a1fjj to #a1hjj pounds1 and passenger-trains from #a1jjj to #a1bjj pounds per foot4 ,any bridge is liable to be traversed by two heavy freight-engines followed by a load of three-quarters of a ton to the foot2 so that if we proportion a bridge to carry #c1jjj pounds per foot for the total engine length1 and one ton per foot for the rest of the bridge1 bearing in mind that any one point may be called upon to sustain #bd1jjj pounds1 and regarding the increase of strain upon short spans due to high speeds1 we have the following loads for different spans exclusive of the weight of the bridge3-- -------------------------- ,,span4 ,,lbs4 ,,per ,,foot4 -------------------------- #ab #g1jjj -------------------------- #ae #f1jjj -------------------------- #bj #d1hjj -------------------------- #be #d1jjj -------------------------- #cj #c1fjj -------------------------- #dj #c1bjj -------------------------- #ej #c1jjj -------------------------- #ajj #b1hjj -------------------------- #bjj #b1fjj -------------------------- #cjj #b1ejj -------------------------- #djj #b1dej -------------------------- #ejj #b1djj -------------------------- ,the above does not vary essentially from the ,english practice1 and is substantially the same as given by the committee of the ,american ,society of ,civil ,engineers4 ,the load which any bridge will be required to carry being determined1 and the general plan and dimensions fixed1 the several strains upon the different members follow by a simple process of arithmetic1 leaving to be determined the actual dimensions of the various parts1 a matter which depends upon the power of different kinds of material to resist different strains4 ,this brings us to the exceedingly important subject of the nature and strength of materials4 ,it has been said that we know what one square inch of iron will hold4 ,like the question of loads above examined1 this is a matter which has been settled1 at any rate within very narrow limits1 by the experience of many years of both ,european and ,american engineers4 ,a bar of the best wrought-iron an inch square will not break under a tensile strain of less than sixty thousand pounds4 ,only a small part of this1 however1 is to be used in practice4 ,a bar or beam may be loaded with a greater weight applied as a permanent or dead-load than would be safe as a rolling or moving weight4 ,a load may be brought upon any material in an easy and gradual manner1 so as not to damage it2 while the same load could not be suddenly and violently applied without injury4 ,the margin for safety should be greater with a material liable to contain hidden defects1 than with one which is not so2 and it should be greater with any member of a bridge which is subjected to several different kinds of strain1 than for one which has to resist only a single form of strain4 ,respect1 also1 should be had to the frequency with which any part is subjected to strain from a moving load1 as this will influence its power of endurance4 ,the rule in structures having so important an office to perform as railroad or highway bridges1 should be1 in all cases1 absolute safety under all conditions4 ,the ,british ,board of ,trade fixes the greatest strain that shall come upon the material in a wrought-iron bridge1 from the combined weight of the bridge and load1 at #e tons per square inch of the net section of the metal4 ,the ,french practice allows #c-h_/aj tons per square inch of the cross section of the metal1 which1 considering the amount taken out by rivet-holes1 is substantially the same as the ,english allowance4 ,the report of the ,american ,society of ,civil ,engineers1 above referred to1 recommends #aj1jjj pounds per inch as the maximum for wrought-iron in tension in railroad bridges4 ,for highway bridges a unit strain of #ae1jjj pounds per square inch is often allowed4 ,a very common clause in a specification is that the factor of safety shall be four1 five1 or six1 as the case may be1 meaning by this that the actual load shall not exceed one-fourth1 one-fifth1 or one-sixth part of the breaking-load4 ,it is a little unfortunate that this term1 factor of safety1 has found its way into use just as it has2 for it by no means indicates what is intended1 or what it is supposed to4 ,the true margin for safety is not the difference between the working-strain and the breaking-strain1 but between the working-strain and that strain which will in any way unfit the material for use4 ,now1 any material is unfitted for use when it is so far distorted by overstraining that it cannot recover1 or1 technically speaking1 when its elastic limit has been exceeded4 ,the elastic limit of the best grades of iron is just about half the breaking-weight1 or from #be1jjj to #cj1jjj pounds per inch4 ,a poor iron will often show a very fair breaking-strength1 but1 at the same time1 will have a very low elastic limit1 and be entirely unfit for use in a bridge4 ,a piece of iron of very inferior quality will often sustain a greater load before breaking than a piece of the best and toughest material1 for the reason that a tough but ductile iron will stretch before giving way1 thus reducing the area of section1 while a hard but poor iron will keep nearly its full size until it breaks4 ,a tough and ductile iron should bend double1 when cold1 without showing any signs of fracture1 and should stretch fifteen per cent of its length before breaking2 but much of the iron used in bridges1 although it may hold #dj1jjj or #ej1jjj pounds per inch before failing1 will not bend over #ij degrees without cracking1 and has an elastic limit as low as #ah1jjj pounds4 ,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-weight4 ,a specification which allowed no material to be strained by more than #aj1jjj pounds per inch1 and no iron to be used with a less elastic limit than #be1jjj pounds1 would1 at the same time1 agree with the standard requirement1 both in ,england and in the ,united ,states1 and would also secure a good quality of iron4 ,two documents published some time since illustrate the preceding remarks4 ,the first is the account of the tests of the iron taken from the ,tariffville bridge after its failure1 and the second is the specification for bridges on the ,cincinnati ,southern ,railroad4 ,the ,tariffville bridge1 though nominally a wooden one1 like most structures of the kind relied entirely upon iron rods to keep the wood-work together4 ,although the rods were too small1 and seriously defective in manufacture1 the bridge ought not to have fallen from that cause4 ,the ultimate strength of the iron was not what it should have been1 but yet it was not low enough to explain the disaster2 but when we look at the quality of the iron1 we have the cause of the fall4 ,the rods taken from the bridge show an ultimate tensile strength of #dg1efj pounds per inch1 but an elastic limit of only #ai1jjj pounds2 while the strain which was at any time liable to come on them was #bb1jjj pounds per inch1 or #c1jjj pounds more than the elastic limit4 ,the fracture of the tested rods1 which1 it is stated1 broke with a single blow of the hammer very much in the manner of cast-iron1 showed a very inferior quality of metal4 ,the rods broke in the bridge exactly where we should look for the failure2 viz41 in the screw at the end4 ,no ordinary inspection would have detected this weakness4 ,no inspection did detect it1 but a proper specification faithfully carried out would have prevented the disaster4 ,look now at an extract from the specification for bridges upon the ,cincinnati ,southern ,railway3-- ,all parts of the bridges and trestleworks must be proportioned to sustain the passage of the following rolling-load at a speed of not less than #cj miles an hour3 viz41 two locomotives coupled1 each weighing #cf tons on the drivers in a space of #ab feet1 the total weight of each engine and tender loaded being #ff tons in a space of #ej feet1 and followed by loaded cars weighing #bj tons each in a space of #bb feet4 ,an addition of #be per cent will be made to the strains produced by the rolling-load considered as static in all parts which are liable to be thrown suddenly under strain by the passage of a rapidly moving load4 ,a similar addition of #ej per cent will be made to the strain on suspension links and riveted connections of stringers with floor-beams1 and floor-beams with trusses4 ,the iron-work shall be so proportioned that the weight of the structure1 together with the above specified rolling-load1 shall in no part cause a tensile strain of more than #aj1jjj pounds per square inch of sectional area4 ,iron used under tensile strain shall be tough1 ductile1 of uniform quality1 and capable of sustaining not less than #ej1jjj pounds per square inch of sectional area without fracture1 and #be1jjj pounds per square inch without taking a permanent set4 ,the reduction of area at the breaking-point shall average #be per cent1 and the elongation #ae per cent4 ,when cold1 the iron must bend1 without sign of fracture1 from #ij to #ahj degrees4 ,a specification like this1 properly carried out1 would put an absolute stop to the building of such structures as the ,tariffville ,bridge1 and would prevent a very large part of the catastrophes which so often shock the community1 and shake the public faith in iron bridges4 ,reference has been made above to the proper loads to be placed upon wrought-iron when under a tensile strain4 ,similar loads have been determined for other materials1 and for other kinds of strain4 ,the preceding remarks in regard to the loads for which bridges should be designed1 and the safe weight to be put upon the material1 are given to show how far the safety of a bridge is a matter of fact1 and how far a matter of opinion4 ,it will be seen that the limits within which we are at liberty to vary1 are quite narrow1 so that bridge-building may correctly be called a science2 and there is no excuse for the person who guesses1 either at the load which a bridge should be designed to bear1 or at the size of the different members of the structure4 ,still less can we excuse the man who not only guesses1 but who1 in order to build cheaply1 persistently guesses on the wrong side4 ,it will1 of course1 be understood1 when it is said that bridge-building may be called a science1 that it can only be so when in the hands of an engineer whose judgment has been matured by wide experience1 and who understands that no mechanical philosophy can be applied to practice which is not subject to the contingencies of workmanship4 ,there are many bridges which will stand the test of figures very well1 and which are nevertheless very poor structures4 ,the general plan of a bridge may be good1 the computations all right1 and yet it may break down under the first train that passes over it4 ,there are many practical considerations that cannot be1 at any rate have not yet been1 reduced to figures4 ,it is not enough that the strains upon each member of a bridge should be correctly estimated1 and fall within the safe limits3 the different members of the bridge must be so connected1 and the mechanical details such1 as to insure1 under all conditions1 the assumed action of the several parts4 ,in fine1 while we can say that a bridge that does not stand the test of arithmetic is a bad bridge1 we cannot always say that a structure which does stand such a test is a good one4 ,we often hear it argued that a bridge must be safe1 since it has been submitted to a heavy load1 and did not break down4 ,such a test means absolutely nothing4 ,it does not even show that the bridge will bear the same load again1 much less does it show that it has the proper margin for safety4 ,it simply shows that it did not break down at that time4 ,every rotten1 worn-out1 and defective bridge that ever fell has been submitted to exactly that test4 ,more than this1 it has repeatedly happened that a heavy train has passed over a bridge in apparent safety1 while a much lighter one passing directly afterwards has gone through4 ,in almost all such cases1 the structure has been weak and defective2 and finally some heavy load passes over1 and cripples the bridge1 so that the next load produces a disaster4 ,for the test of a bridge to be in any way satisfactory1 we must know just what effect such test has had upon the structure4 ,we do not find this out by simply standing near1 and noting that the bridge did not break down4 ,we must satisfy ourselves beyond all question that no part has been overstrained4 ,a short time ago the builders of a wretchedly cheap and unsafe highway bridge1 in order to quiet a fear which had arisen that the structure was not altogether sound1 tested a span #abb feet long with a load of #eh1jjj pounds2 and inasmuch as the bridge did not break down under this load1 which was less than a quarter part of what it was warranted to carry safely1 the county commissioners considered the result eminently satisfactory1 and remarked that the test was made merely to satisfy the public that the bridge was abundantly safe for all practical uses4 ,the public would1 no doubt1 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 it1 and yet that very bridge broke down directly afterwards under a passenger-train4 ,now1 according to the common notion1 that was a good bridge in the morning1 and a very bad bridge1 or rather1 no bridge at all1 in the evening4 ,the question for the public is1 ,when did it cease to be a good bridge1 and begin to be a bad one8 ,a test like the one referred to above can do no more than illustrate the ignorance or lack of honesty of those who make it1 or those who are satisfied with it4 ,such a test might come within a dozen pounds of breaking the bridge down1 and no one be the wiser4 ,the entire absurdity of such testing has recently been illustrated in the most decided manner4 ,the very same company that built the bridge above referred to1 made also another one on exactly the same plan1 and of almost precisely the same size1 and tested it when done by placing almost exactly the same load upon it4 ,the bridge did not break down2 and the county commissioners1 for whom the work was done1 were satisfied that it was abundantly safe for all practical uses1 accepted it1 paid for it2 and in less than ten years it broke down under a single team and a little snow1 weighing in all not over one-tenth part of the load the bridge was warranted to carry1 and not over one-half the load with which it had been previously tested4 ,if this bridge had been tested by five minutes of honest arithmetic1 it would have been promptly condemned the very day it was finished4 ,in view of the preceding1 what shall we say of a bridge company that deliberately builds a bridge in the middle of a large town1 where it will be subjected to heavy teaming1 and1 owing to its peculiar location1 to heavy crowds1 and warrants to the town that it shall safely hold a ton per running-foot1 when the very simplest computation shows beyond chance of dispute that such a load will strain the iron to #dj1jjj pounds per square inch8 ,we are to say1 either that such a company is so ignorant that it does not know the difference between a good bridge and a bad one1 or else so wicked as to knowingly subject the public to a wretchedly unsafe bridge4 ,the case referred to is not an imaginary one1 but existed recently in the main street of a large ,new-,england town4 ,the joints in that bridge1 which could safely hold but #bj1jjj pounds1 were required to hold #fj1jjj pounds under the load which the builders had warranted the bridge to carry safely4 ,the case was so bad1 that1 after a lengthy controversy1 the town officers had a thorough expert examination of the bridge1 which promptly condemned it as in imminent danger of falling1 and as having a factor of safety of only #a-ae_/ajj1 which is practically no factor at all4 ,notwithstanding all this1 and in the face of the report1 the president of the bridge company came out with a letter in the papers1 in which he pronounced the bridge perfectly safe4 ,thus we actually have the president of a bridge company in this country stating openly that a factor of safety of #a-ae_/ajj makes a bridge perfectly safe1 or1 in other words1 that a bridge can safely bear the load that will break it down1 for he very wisely made not the slightest attempt to disprove any of the conclusions of the commission2 and this company has built hundreds of highway bridges all over the ,united ,states1 and is building them to-day wherever it can find town or county officers ignorant enough to buy them4 ,it might be supposed1 that1 under the above condemnation1 the authorities controlling the bridge would have taken some steps to prevent the coming disaster4 ,they did1 however1 nothing of the kind1 but allowed the public to travel over it for more than a year1 at the most fearful risk1 until public indignation became so strong that a special town-meeting was called1 and a committee appointed to remove the old bridge1 and to build a new one4 ,one of the worst cases of utterly dishonest bridge-building that we have had of late years in ,massachusetts1 was that of the iron highway bridge across the ,merrimac ,river at ,groveland1 a few miles below ,haverhill1 one span of which broke down in ,january1 #ahha4 ,this bridge was built in #ahga-ahgb1 and consisted of #f spans1 each about #abe feet long4 ,the whole cost of the structure was #hj1jjj1 and the contract price for the iron-work was #bh1jjj4 ,the company which made that bridge1 agreed in their contract to give the county a structure that should carry safely #c1jjj pounds per running-foot besides its own weight2 but they built a bridge1 which1 if they knew enough to compute its strength at all1 they knew perfectly well could not safely carry over one-quarter part of that load4 ,in fact1 the weight of the bridge alone is more than it ever ought to have borne4 ,the company warranted each span of that bridge to carry safely a net or moving load of #afe tons1 and it broke down under a single team and a small amount of snow4 ,the company warranted that bridge to carry safely a load which would strain the iron to #ej1jjj pounds per inch1 when it knew perfectly well that #ae1jjj pounds per inch was the most that could safely be borne4 ,there are several concerns in the ,united ,states which make a specialty of highway bridges1 and which1 taking advantage of the ignorance of public officials1 are flooding the country with bridges no better than that at ,groveland4 ,on an average1 at least twenty of these miserable traps tumble down every year1 and nothing is done to bring the guilty parties to punishment4 ,dishonest builders cheat ignorant officials1 and the public suffers the damage and pays the bills4 ,is human life worth enough to pay for having these structures inspected1 and1 if found unsafe1 strengthened or removed8 ,can we do any thing to prevent towns and counties from being imposed upon by dishonest builders8 ,we certainly can1 if those who control these matters care enough about it to do it4 ,there are two ways of buying a bridge1--a good way and a bad one2 and these two ways are so plain that no one can misunderstand4 ,to buy a bad bridge1 just as soon as your town or county votes money for a new bridge1 certain agents--and they are as numerous as the agents for sewing-machines or lightning-rods--will call on1 or write to1 the town or county officers1 and will offer to build any thing under heavens you want of any size1 shape1 or material1 and for almost any price4 ,they will produce testimonials from all the town and county officers in the country for the excellence of their bridges1 and would not hesitate to give reference1 even1 for their moral character1 if you should ask it4 ,if they find that you don't know any thing about bridges1 they will1 to save you the trouble1 furnish a printed specification2 which document will commit you to pay the money1 but will not commit the bridge company to any thing at all4 ,when the bridge is put up1 you never will know whether the iron is good or bad1 nor whether the dimensions and proportions are such as to be safe or not4 ,you will know that you have paid your money away1 but you never will know what you have got for it until some day when your bridge gets a crowd upon it1 and breaks down1 and you have the damage to pay4 ,this mode of buying a bridge is very common4 ,to buy a good bridge1 first determine precisely what you want2 and if you don't know any thing in regard to bridge-building yourself1 employ an engineer who does1 to make a specification stating exactly what you want1 and what you mean to have4 ,then advertise for bridge-builders to send in plans and proposals4 ,let the contractors understand that all plans and computations are to be submitted to your engineer1 that all materials and workmanship will be submitted to your inspectors1 and that the whole structure is to be made subject to the supervision of a competent engineer1 and accepted by him for you4 ,you will find at once1 that1 under such conditions1 all travelling agents and builders of cheap bridges will avoid you as a thief does the light of day4 ,you will have genuine proposals from responsible companies1 and their bids should be submitted to your engineer4 ,when you have made your choice1 let the contract be written by your lawyer1 and have the plans and specifications attached4 ,employ a competent engineer to inspect the work as it goes on2 and when it is done1 you will have a bridge which will be warranted absolutely sound by the best authority4 ,this mode of buying a bridge is very uncommon4 ,the ,ashtabula bridge1 it is stated in the report of the committee of the ,ohio ,legislature appointed to investigate that disaster1 had factors1--we can hardly call them factors of safety1--in some parts as low as #a-f_/aj and #a-b_/aj1 such factors referring to the breaking-weight2 and even these factors were obtained by assuming the load as at rest1 and making no allowance for the jar and shock from a railroad train in motion4 ,well may the commissioners say1 as they do at the end of their report1 ,the bridge was liable to go down at any time during the last ten years under the loads that might at any time be brought upon it in the ordinary course of the company's business1 and it is most remarkable that it did not sooner occur4 ,one point always brought forward when an iron bridge breaks down1 is the supposed deterioration of iron under repeated straining2 and we are gravely told that after a while all iron loses its fibre1 and becomes crystalline4 ,this is one of the mysteries which some persons conjure up at tolerably regular intervals to cover their ignorance4 ,it is perfectly well known by engineers the world over1 that with good iron properly used1 nothing of the kind ever takes place4 ,this matter used to be a favorite bone of contention among engineers1 but it has long since been laid upon the shelf4 ,no engineer at the present day ever thinks of it4 ,we have only to allow the proper margin for safety1 as our first-class builders all do1 and this antiquated objection at once vanishes4 ,the examples of the long duration of iron in large bridges are numerous and conclusive4 ,the ,niagara-,falls railroad suspension bridge was carefully inspected after twenty-five years of continued use under frequent and heavy trains1 and not only was it impossible to detect by the severest tests any defect in the wire of the cables1 but a piece of it1 being thrown upon the floor1 curled up1 showing the old kink which the iron had when it was first made1 and wound on the reel4 ,the ,menai suspension bridge1 in which #a1jjj tons of iron have hung suspended across an opening of #fjj feet for sixty years1 shows no depreciation that the most rigid inspection could detect4 ,iron rods1 recently taken from an old bridge in this country1 have been carefully tested after sixty years of use1 and found to have lost nothing1 either of the original breaking-strength1 or of the original elasticity4 ,the question is frequently asked1 ,does not extreme cold weaken iron bridges8 ,to this1 it may be replied1 that no iron bridge1 made by a reliable company1 has ever shown the slightest indication of any thing of the kind1 though they have been used for many years in ,russia1 ,norway1 ,sweden1 and ,canada1 and nothing that we know in regard to iron gives us any reason to suppose that any thing of the kind ever will happen4 ,but here1 again1 every thing turns upon the quality of the iron4 ,iron containing phosphorus is cold-short1 or brittle when cold1 and will break quicker under repeated and sudden shocks in cold weather than when it is warm4 ,with good iron1 properly used1 we need have no fear on this point4 ,the securing such iron is a matter to which the utmost attention is paid by our first-class bridge-building firms1 but it is a matter to which no attention is paid by the builders of cheap bridges4 ,we might suppose that a person1 in putting an insufficient amount of iron into a bridge1 would be careful to get the best quality2 but exactly the reverse seems to be the case1 on the ground1 perhaps1 that the less of a bad thing we have1 the better4 ,many persons1 in building wooden bridges1 take no pains to get iron rods which are suitable for such work1 but purchase what is easiest to be had in the market1 and in many cases never find that the iron was bad until a bridge tumbles down4 ,there are1 without the slightest question1 hundreds of bridges now in use in this country1 which1 as far as mere proportions and dimensions go1 would appear to be entirely safe1 but which1 on account of the quality of the iron with which they are made1 are entirely unsafe2 and there always will be1 as long as public officials purchase iron which they know nothing about1 to put into bridges4 ,when a bridge is finished1 the ordinary examinations never detect the quality of the iron2 so that the wise remarks of many inspectors1 or the opinions of those in charge of these structures1 as to the exact condition of a bridge1 are of little or no value4 ,we often hear iron bridges condemned1 while wooden ones1 so called1 are supposed to be free from defects4 ,it does not seem to occur to persons holding such ideas1 that wooden bridges rely just as much upon the strength of the iron rods that tie the timbers together1 as upon the timber4 ,as a matter of fact1 where one iron bridge falls1 a dozen wooden ones do the same thing4 ,one very decided advantage which an iron bridge has over a wooden one1 is that we can make sure of good iron in the beginning1 and that we can also be sure that it does not decay2 while1 however good our timber may be in the beginning1 we never can be entirely sure of its condition afterwards4 ,there are wooden bridges now standing in this country1 all the way from sixty to eighty years old1 which are apparently as good as ever2 while there are others1 not ten years old1 which are so rotten as to be unfit for use4 ,it will not do to assume1 that1 because no defects are very evident in a wooden bridge1 therefore it has none4 ,when a wooden bridge1 originally made of only fair material1 has been in use under railroad trains for twenty-five or thirty years1 and in a position where timber would naturally decay1 we are bound to suspect that bridge4 ,to assume such a bridge to be all right until we can prove it to be all wrong1 is not safe4 ,to assume a bridge to be all wrong until we can prove it to be all right1 is a safe method1 though not a popular one4 ,any person who has had occasion to remove old wooden bridges1 will recall how often they look very much worse than was anticipated4 ,there is one defect in railway bridges which has often led to the most fearful disasters1 and which1 without the slightest question1 can be almost entirely1 if not entirely1 removed1 and at a moderate cost4 ,at least half the most disastrous failures of railroad bridges in the ,united ,states have been due to a defective system of flooring4 ,with a very large proportion of our bridges1 the failure of a rail1 the breaking of an axle1 or any thing which shall throw the train from the track1 is almost sure to be followed by the breaking down of the bridge4 ,the cross-ties are in many cases very short1 and the floor is proportioned for a train on and not off the rails4 ,when an engine on such a floor leaves the track1 it plunges off the ends of the cross-ties into the open space between the stringers and the chords1 and generally wrecks the bridge4 ,to prevent this1 the cross-ties should be long and well supported1 and placed so close that a derailed engine cannot cut through them4 ,the track should also be provided with guard-timbers well fastened1 and the width between the trusses should be so great that the wheels of a derailed train will be stopped by the guard-rail before the side of the widest car can strike the truss4 ,the importance of a substantial floor system has been very fully recognized by the railroad commissioners of ,massachusetts1 who have recently issued a very suggestive circular1 accompanied by numerous examples of track construction for railway bridges4 ,if this circular receives proper attention1 it is sure to produce good results4 ,another point which has often been neglected1 is making sufficient provision to resist the force of the wind4 ,a tornado1 such as is not uncommon in this country1 will exert a force of #dj pounds per square foot1 which upon the side of a wooden bridge1 say of #bjj feet span1 and #be feet high1 and boarded up as many bridges are1 would amount to a lateral thrust of no less than #ajj tons2 and this load would be applied in the worst possible manner1 i4e41 in a series of shocks4 ,there have been many cases in this country where bridges have been blown down2 and a case recently occurred where an iron railroad bridge of #ahj feet span1 and #cj feet high1 and presenting apparently almost no surface to the wind1 was blown so much out of line that the track had to be shifted4 ,the recent terrible disaster at the ,firth of ,tay was1 no doubt1 due to this cause4 ,at the time of the ,tariffville catastrophe1 it was gravely stated at the coroner's inquest1 and by railroad officers who claimed to know about such things1 that the disaster was caused by the tremendous weight of two locomotives which were coupled together1 and it was stated that one engine would have passed in safety2 and directly afterwards the superintendent of a prominent railroad in ,new ,england issued an order forbidding two engines connected to pass over any iron bridges4 ,it is all very well for a company to issue such an order1 so far as it may give the public to understand that it is determined to use every precaution against disaster2 but such an order may have the effect of creating a distrust which really ought not to exist4 ,if a railway bridge is not entirely safe for two engines1 it is certainly entirely unsafe for one engine and the train following2 the only saving in weight by taking off one engine being the difference between the weight of that engine and the weight of the cars that would occupy the same room4 ,for example1 a bridge of #bjj feet span will weigh #a1ejj pounds per lineal foot4 ,an engine and its tender will weigh #fj tons in a length of #ej feet1 and a loaded freight-train may easily weigh #b_/c of a ton per lineal foot4 ,the total weight of the span1 with two engines1 and the rest of the bridge covered with loaded freight-cars1 would thus be #cbj tons4 ,if we take off one engine1 and fill its place with cars1 we take off #fj tons1 and put in its place #cc tons2 i4e41 we remove #bg tons1 or just about #a_/ab of the working-load4 ,taking off a large part of the working-load1 however1 is taking off a very small part of the breaking-load2 with a factor of safety of six1 for example1 taking off #a_/ab of the working-load is taking off less than #a_/gj of the breaking-load4 ,an order1 therefore1 like that above1 can only be of use when the working-load and the breaking-load are so nearly alike that the actual load is a dangerous one3 that is when the bridge is unfit for any traffic whatever2 so that1 if such an order was really needed1 it would1 in itself1 be1 in the eyes of an engineer1 a condemnation of the bridge4 ,having seen something of the structures which require inspecting1 let us now see what kind of inspection we have in this country1 and the result of it2 and let us also see the inspection which we might have1 and the results that might be produced4 ,looking first at railroad bridges1 it might be supposed that no one could be so much interested in keeping such structures in good order as the companies which own those bridges1 and which have the bills to pay in case of disaster4 ,this is1 of course1 so2 but1 in spite of the fact1 the ,ashtabula bridge broke down1 on one of the best managed lines in the country1 and cost the company over half a million dollars in damages4 ,no railroad bridge ever broke down1 which the owners were not interested in keeping safe2 but there is always a desire to put off incurring large expenses until the last moment1 and thus weak bridges are very often let go too long4 ,a short time since1 the superintendent of a large railroad stated plainly before a legislative committee1 that many of the smaller roads were not safe to run over1 but that such roads were having a hard time1 and could not afford to keep their track and bridges in a safe condition4 ,during the past ten years over two hundred railroad bridges in the ,united ,states have broken down4 ,these bridges were all kept under such inspection as the railroad companies owning them considered sufficient1 or such as they could afford2 but either the supervision was defective1 or the companies knowingly continued the use of unsafe bridges1 and this fault has by no means been confined to the smaller and poorer roads4 ,it would seem1 therefore1 that inspection by the companies themselves has not been sufficient4 ,it certainly has not been enough to prevent two hundred disasters in ten years4 ,it is the custom in several of the ,united ,states to maintain what is termed a railroad commission4 ,the original intention seems to have been for these commissions to keep the railroads under some kind of inspection1 and in some way to assist in settling any questions that might arise between different companies1 and between railroad companies and the public4 ,as far as we can judge by the results produced1 in the ,states where these commissions have been established1 we can hardly pronounce them of any very great importance4 ,in many ,states1 it is very certain1 that1 in regard to matters of inspection1 the work of these boards has been simply a farce2 and it could hardly be otherwise in a ,state which pays its commissioners only #a1jjj salary1 or1 worse yet1 as in some cases1 only #ejj4 ,add to this1 that in many cases the appointments have been purely political ones1 and we can see the absurdity of expecting any results of value4 ,we should hardly suppose that three men1 in many cases entirely unacquainted with mechanical matters1 could by riding over a railroad once or twice a year1 occasionally getting out to examine the paint on the outside of the boards1 which conceal a truss from view1 judge very correctly of the elastic limit of the iron rods which they have never seen1 and of which they do not even know the existence4 ,for ample proof of the utter inefficiency of the present system1 we have only to compare the reports of the railroad commissioners in almost any ,state1 with the actual condition of the structures described4 ,in one ,state a late annual report covers a whole railroad with the remark1 ,all of the bridges on this line are in excellent order2 and yet there were at that very time1 and are now1 on that road1 several large wooden bridges with a factor of safety referred to the breaking-weight of not over two under a fair load1 assuming the iron rods to be of the very best material1--a point upon which there is no evidence whatever4 ,there is1 in fact1 no difference which any ordinary inspection would detect between these bridges as they stand to-day1 and the ,tariffville bridge as it stood the day before it fell4 ,in another ,state1 an iron bridge is in use under heavy trains1 which has a factor of only #b-a_/b instead of #f1 and yet the ,state report pronounces it an excellent structure and a credit to the railroad company1 which recklessly allows its trains to pass over it4 ,in yet another ,state1 the commissioners in #ahgd reported that a certain bridge should be removed2 and this was quite correct1 as it was an eminently unsafe bridge4 ,in #ahge they suggested the same thing again4 ,in #ahgf they say1 ,this bridge must be rebuilt the coming spring4 ,in #ahgg they again reported1 ,this bridge must be rebuilt before the spring opens4 ,it is old1 and will not be safe for the passage of trains over it1 if the ice or freshet should take away the temporary trestles1 which now in a great measure support the truss4 ,a year later than that1 in #ahgh1 a public protest was made against the further use of that bridge1 as the lower chords were rotten1 broken1 pulled apart1 and the only thing that held it up was a trestle1 liable at any time to be knocked out by the ice2 and yet1 after all this1 in reply to the protest1 the commissioners replied that they had just tested the bridge by running an engine over it1 and pronounced it safe for the present1 whatever that may mean4 ,now1 just how it was that this bridge1 which was old1 rotten1 and worn out1 which the commissioners themselves had condemned for four successive years1 which they had said two years before must be rebuilt the coming spring1 and which relied entirely upon a trestle liable at any time to be carried away1 had suddenly become safe for the present1 is not plain to see4 ,evidently such inspection as this is of no value4 ,it is exactly this utterly incompetent and dishonest inspection1 this guessing that a bridge will stand until it falls1 that lies at the bottom of half the disasters in the country4 ,it is under exactly such inspection that those wretched traps1 the ,ashtabula and ,tariffville bridges1 fell1 and killed over one hundred people4 ,no wonder that railroad officials have an undisguised contempt for ,state inspection4 ,while in a few ,states the inspection is not quite so bad as that referred to1 as a general thing it is no better2 and we have no right to expect any thing better under the present system4 ,the ,state inspection which we have had throughout this country has not prevented the breaking down of one hundred bridges in the past ten years4 ,twenty-five ,states have railroad commissions2 but in nine of them the commission consists of only a single man1 who1 in some cases1 is paid only #ejj a year4 ,a ,state can pay #ejj a year for having its bridges inspected1 and it will get such service as never did and never will prevent a disaster2 or it can pay a good price for competent inspection1 which will be worth ten times the money to the ,state4 ,the money which the ,lake ,shore ,railroad paid in damages for the ,ashtabula disaster alone1 would have employed permanently six men at #e1jjj a year each1 and a hundred lives would have been saved besides4 ,with regard to highway bridges1 we are1 if possible1 even worse off than in regard to railway bridges2 for in the case of such structures1 neither the owners nor the ,state make any pretence at inspection4 ,it is impossible to say how many highway bridges have broken down during the past ten years1 but it is estimated by bridge-builders that the number cannot be less than two hundred4 ,this is1 no doubt1 far within the truth2 and by far the larger part of these structures are not old wooden bridges1 but are new bridges of iron4 ,if we knew positively that in just six months a terrible disaster would occur under the present system of bridge inspection1 and knew also1 that1 by a better system1 such disaster would certainly be prevented1 it is possible that a change might be made4 ,we know that a proper method of building and inspecting bridges would certainly have prevented the disasters at ,ashtabula1 ,tariffville1 and ,dixon4 ,we know that the inspection which those bridges received1 did not prevent three of the most fearful disasters the country has ever seen4 ,admitting1 now1 that structures so important to the public safety as bridges1 both upon roads and railroads1 ought to be kept under rigid inspection and control1 and that no system at present existing has been able to prevent the most fearful catastrophes1 what shall we do8 ,directly after the ,ashtabula disaster1 the ,ohio legislative committee1 appointed to investigate that affair1 presented to the ,legislature a bill1 ,to secure greater safety for public travel over bridges1 in which was plainly specified the loads for which all bridges should be proportioned1 the maximum strains to which the iron should be subjected1 and a method for inspecting the plans of all bridges before building1 and the bridges themselves during and after construction4 ,the governor1 with the consent of the ,senate1 was to appoint the inspector for a term of five years at a salary not exceeding #c1jjj a year1 such inspector to pass a satisfactory examination before a committee of the ,american ,society of ,civil ,engineers1 themselves practical experts in bridge construction1 and he was also to take a suitable oath for the faithful performance of his duty4 ,this bill never became a law4 ,an appropriation was made for a short time to pay for certain examinations1 and there the matter stopped4 ,the committee of the ,american ,society of ,engineers were not agreed upon this matter4 ,messrs4 ,james ,b4 ,eads and ,charles ,shaler ,smith suggested the appointment in each ,state of an expert1 to whom all plans should be submitted1 and by whom all work should be inspected1--such expert to have been examined and approved by the ,american ,society of ,civil ,engineers4 ,the inspector was also to visit the scene of every accident1 so called1 and to ascertain1 as far as possible1 the cause4 ,messrs4 ,t4 ,c4 ,clarke and ,julius ,w4 ,adams believed1 that1 in the present state of public opinion1 the above method would be impracticable1 and feared1 that1 if inspectors were appointed1 it would be by political influence1 and that the result would be worse than at present1 as the inspectors would be inefficient1 and yet1 to a great extent1 would relieve the owners of bad bridges from legal responsibility4 ,they held that the best that could be done would be to provide means1 in case of disaster1 to fix plainly the responsibility1 and recommended1 ,first1 that the standard for strength fixed by the ,society should be the legal standard2 and1 in case it should be found that any bridge was of less strength than this1 it should be taken as prima facie evidence of neglect on the part of the owners4 ,second1 that no bridge should be opened to the public until a plan giving all dimensions1 strains1 and loads1 sworn to by the designers and makers1 and attested by the corporation having control of it1 had been deposited with the ,american ,society2 and further1 that the principal pieces of iron in the bridge should be stamped with the name of the maker1 place of manufacture1 and date4 ,messrs4 ,a4 ,p4 ,boller and ,charles ,macdonald looked rather toward effecting the desired result by so directing public sentiment by keeping the correct standard for bridges before it1 that it would eventually compel the passage of the necessary laws4 ,whether it is possible1 in this country1 to make an appointment dependent purely upon honesty and capacity1 and free from political influence1 may well be doubted4 ,no competent engineer would be willing to accept a position which would place upon him so great a responsibility1 except under a very carefully devised plan4 ,a very considerable force of inspectors would be required to carry out a system which should produce the desired result4 ,the amount of work to be done at the commencement would be very great1 as no proper inspection has ever been made of the greater part of the bridges in the country1 of which the number is very large4 ,if any such plan as above suggested should be found feasible1 the inspectors should have in their possession a complete set of plans of every bridge of importance in the ,state1 with all the computations of its strength1 and as complete a history of each structure from its commencement as can be made up1 all this to be supplemented by periodic examinations4 ,if1 from such records1 we find that a bridge was made of ordinary green timber twenty-five years ago1 and that it has been getting rotten ever since2 that it has rods of common merchant iron that were bought by some person1 not specially acquainted with the business1 from an unknown firm1--we had better pull it down before it falls4 ,if1 from such records1 we find an iron bridge built twenty-five years ago by an unknown company1 with iron1 at best1 of a doubtful quality1 and having a factor of three or four for the rolling-stock and speeds of twenty years ago1 instead of a factor of six for the rolling-stock and speeds of to-day1 we had better remove that bridge before it removes itself4 ,such a record would be the property of the ,state1 always accessible to any one1 and would be handed down1 so that the knowledge of one person would not expire with his term of office4 ,no bridge should be erected in any ,state without first submitting the plans to the inspector1 and receiving his approval1 and depositing with him a complete set of the plans and computations for the work4 ,by this approval is not meant that the inspector is merely to give a favorable opinion as to the plan1 but that he is to find1 as a matter of fact1 whether the proposed dimensions and proportions are such as will make a safe bridge--and just what a safe bridge is1 can be plainly defined by law1 as it is in ,europe1 and as it has been proposed by the ,american ,society of ,civil ,engineers4 ,for example1 if the law says that an iron railway bridge of #ajj feet span shall be proportioned to carry a load of #c1jjj pounds per lineal foot besides its own weight1 and that1 with such a load1 no part shall be strained by more than #aj1jjj pounds per inch1 all the inspector has to do is to go over the figures1 and see that the dimensions given on the plan are such as will enable the bridge to carry the load without exceeding the specified strains4 ,when the work is erected1 the inspection must show that the plan has been exactly carried out1 that the details are good1 and proper evidence of the quality of the material used should also be given4 ,such inspection as this would at once prevent the erection of bridges like those at ,ashtabula and ,tariffville1 and would save the public from such traps as those that fell at ,dixon and at ,groveland4 ,perhaps the most difficult thing to do will be to get satisfactory evidence in regard to the bridges that have been for a considerable time in use1 and of which we do not know the history4 ,this will be especially true in regard to the wooden bridges1 of which there are so many about the country4 ,not only is it very difficult to be sure of the exact condition of the timber1 but it is equally hard to tell any thing about the iron4 ,the ,tariffville bridge fell on account of defective iron1 and the defect was of such a nature as to defy any ordinary inspection4 ,what do we know to-day of the quality of the iron rods in any wooden bridge in ,massachusetts8 ,it is very doubtful if the best inspection we have in the ,united ,states at the present time would have found any defect so evident in the ,tariffville bridge as to condemn it as unfit for the passage of trains4 ,there are hundreds of exactly such bridges all over ,new ,england1 as far as we can tell by the best inspection we now have1 made on the same plan1 with no more material1 and of which we know just as little of the quality of the iron as we did in the ,tariffville bridge4 ,of course we cannot expect to get a perfect system all at once4 ,any plan which might be proposed would1 no doubt1 be found more or less defective at first4 ,we can hardly get a system worse than the one we now have1 which allows forty bridges to break down every year4 ,we may get a better one4 ,to make the public see the need of such a system is the first step to be taken4 99 99 99 99 99 ,,lee ,,and ,,shepard',s ,,popular ,,handbooks4 ,price1 each1 in cloth1 #ej cents1 except when other price is given4 ,forgotten ,meanings2 or an ,hour with a ,dictionary4 ,by ,,alfred ,,waites1 author of ,historical ,student's ,manual4 ,handbook of ,elocution ,simplified4 ,by ,,walter ,k4 ,,fobes1 with an ,introduction by ,,george ,m4 ,,baker4 ,handbook of ,english ,synonyms4 ,with an ,appendix1 showing the ,correct ,use of ,prepositions2 also a ,collection of ,foreign ,phrases4 ,by ,,loomis ,j4 ,,campbell4 ,handbook of ,conversation4 ,its ,faults and its ,graces4 ,compiled by ,,andrew ,p4 ,,peabody1 ,d4 ,d41 ,,ll4 ,d4 ,comprising3 7#a7 ,dr4 ,,peabody',s ,address2 7#b7 ,mr4 ,,trench',s ,lecture2 7#c7 ,mr4 ,,parry ,,gwynne',s ,a ,word to the ,wise2 or1 ,hints on the ,current ,improprieties of ,expression in ,reading and ,writing2 7#d7 ,mistakes and ,improprieties of ,speaking and ,writing ,corrected4 ,handbook of ,punctuation and other ,typographical ,matters4 ,for the ,use of ,printers1 ,authors1 ,teachers1 and ,scholars4 ,by ,,marshall ,t4 ,,bigelow1 ,corrector at the ,university ,press1 ,cambridge1 ,mass4 ,handbook of ,blunders4 ,designed to prevent #a1jjj common blunders in writing and speaking4 ,by ,,harlan ,h4 ,,ballard1 ,a4 ,m41 ,principal of ,lenox ,academy1 ,lenox1 ,mass4 ,broken ,english4 ,a ,frenchman's ,struggle in the ,english ,language4 ,instructive as a handbook of ,french conversation4 ,by ,professor ,e4 ,c4 ,,dubois4 ,beginnings with the ,microscope4 ,a working handbook containing simple instructions in the art and method of using the microscope1 and preparing articles for examination4 ,by ,,walter ,p4 ,,manton4 ,field ,botany4 ,a ,handbook for the ,collector4 ,containing instructions for gathering and preserving ,plants1 and the formation of an ,herbarium4 ,also complete instructions in ,leaf ,photography1 ,plant ,printing1 and the ,skeletonizing of ,leaves4 ,by ,,walter ,p4 ,,manton4 ,taxidermy without a ,teacher4 ,comprising a complete manual of instructions for ,preparing and ,preserving ,birds1 ,animals1 and ,fishes1 with a chapter on ,hunting and ,hygiene2 together with instructions for ,preserving ,eggs1 and ,making ,skeletons1 and a number of valuable recipes4 ,by ,,walter ,p4 ,,manton4 ,insects4 ,how to ,catch and how to ,prepare them for the ,cabinet4 ,a ,manual of ,instruction for the ,field-,naturalist4 ,by ,w4 ,p4 ,,manton4 ,what is to be ,done8 ,a ,handbook for the ,nursery1 with ,useful ,hints for ,children and ,adults4 ,by ,,robert ,b4 ,,dixon1 ,m4 ,d4 ,whirlwinds1 ,cyclones1 and ,tornadoes4 ,by ,,william ,,morris ,,davis1 ,instructor in ,harvard ,college4 ,illustrated4 ,mistakes in ,writing ,english1 and ,how to ,avoid ,them4 ,for the use of all who ,teach1 ,write1 or ,speak the language4 ,by ,,marshall ,t4 ,,bigelow4 ,sold by all booksellers1 and sent by mail1 postpaid1 on receipt of price4 ,,lee ,,and ,,shepard ,publishers ,boston 99 99 99 99 99 ,,lee ,,and ,,shepard',s ,,popular ,,handbooks ,price1 each1 in cloth1 #ej cents1 except when other price is given4 ,warrington's ,manual4 ,a ,manual for the ,information of ,officers and ,members of ,legislatures1 ,conventions1 ,societies1 etc41 in the practical governing and membership of all such bodies1 according to the ,parliamentary ,law and ,practice in the ,united ,states4 ,by ,w4 ,s4 ,,robinson 7,warrington74 ,practical ,boat-,sailing4 ,by ,,douglas ,,frazar4 ,classic size1 #a4jj4 ,with numerous diagrams and illustrations4 ,handbook of ,wood ,engraving4 ,with practical instructions in the art1 for persons wishing to learn without an instructor4 ,by ,,william ,a4 ,,emerson4 ,illustrated4 ,price #a4jj4 ,five-,minute ,recitations4 ,selected and arranged by ,,walter ,k4 ,,fobes4 ,five-,minute ,declamations4 ,selected and arranged by ,,walter ,k4 ,,fobes4 ,five-,minute ,readings for ,young ,ladies4 ,selected and adapted by ,,walter ,k4 ,,fobes4 ,educational ,psychology4 ,a ,treatise for ,parents and ,educators4 ,by ,,louise ,,parsons ,,hopkins1 ,supervisor in ,boston ,public ,schools4 ,the ,nation in a ,nutshell4 ,a ,rapid ,outline of ,american ,history4 ,by ,,george ,,makepeace ,,towle4 ,english ,synonymes ,discriminated4 ,by ,,richard ,,whately1 ,d4 ,d41 ,archbishop of ,dublin4 ,a new edition4 ,hints on ,writing and ,speech-making4 ,by ,,thomas ,,wentworth ,,higginson4 ,arithmetic for ,young ,children4 ,being a series of ,exercises exemplifying the manner in which ,arithmetic should be taught to young children4 ,by ,,horace ,,grant4 ,american ,edition4 ,edited by ,,willard ,,small4 ,bridge ,disasters in ,america4 ,the ,cause and the ,remedy4 ,by ,prof4 ,,george ,l4 ,,vose4 ,a ,few ,thoughts for a ,young ,man4 ,by ,,horace ,,mann4 ,a new ,edition4 ,handbook of ,debate4 ,the ,character of ,julius ,csar4 ,adapted from ,j4 ,,sheridan ,,knowles4 ,arranged for ,practice in ,speaking1 for ,debating ,clubs1 and ,classes in ,public and ,private ,schools4 ,sold by all booksellers1 and sent by mail1 postpaid1 on receipt of price4 ,,lee ,,and ,,shepard ,publishers ,boston 99 99 99 99 99 ,,lee ,,and ,,shepard',s ,,popular ,,handbooks4 ,price1 each1 in cloth1 #ej cents1 except when other price is given4 ,exercises for the ,improvement of the ,senses4 ,for ,young ,children4 ,by ,,horace ,,grant1 author of ,arithmetic for ,young ,children4 ,edited by ,,willard ,,small4 ,hints on ,language in connection with ,sight-,reading and ,writing in ,primary and ,intermediate ,schools4 ,by ,s4 ,,arthur ,,bent1 ,a4 ,m41 ,superintendent of ,public ,school1 ,clinton1 ,mass4 ,the ,hunter's ,handbook4 ,containing lists of provisions and camp paraphernalia1 and hints on the fire1 cooking utensils1 etc42 with approved receipts for camp-cookery4 ,by ,,an ,,old ,,hunter4 ,universal ,phonography2 or1 ,shorthand by the ,allen ,method4 ,a self-instructor4 ,by ,g4 ,g4 ,,allen4 ,hints and ,helps for those who ,write1 ,print1 or ,read4 ,by ,b4 ,,drew1 proof-reader4 ,pronouncing ,handbook of ,three ,thousand ,words often ,mispronounced4 ,by ,r4 ,,soule and ,l4 ,j4 ,,campbell4 ,short ,studies of ,american ,authors4 ,by ,,thomas ,,wentworth ,,higginson4 ,the ,stars and the ,earth2 or1 ,thoughts upon ,space1 ,time1 and ,eternity4 ,with an introduction by ,,thomas ,,hill1 ,d4 ,d41 ,,ll4 ,d4 ,handbook of the ,earth4 ,natural ,methods in ,geography4 ,by ,,louisa ,,parsons ,,hopkins1 teacher of ,normal ,methods in the ,swain ,free ,school1 ,new ,bedford4 ,natural-,history ,plays4 ,dialogues and ,recitations for ,school ,exhibitions4 ,by ,,louisa ,p4 ,,hopkins4 ,the ,telephone4 ,an account of the phenomena of ,electricity1 ,magnetism1 and ,sound1 with directions for making a speaking-telephone4 ,by ,professor ,a4 ,e4 ,,dolbear4 ,lessons on ,manners4 ,by ,,edith ,e4 ,,wiggin4 ,water ,analysis4 ,a ,handbook for ,water-,drinkers4 ,by ,g4 ,l4 ,,austin1 ,m4 ,d4 ,handbook of ,light ,gymnastics4 ,by ,,lucy ,b4 ,,hunt1 instructor in gymnastics at ,smith 7female7 ,college1 ,northampton1 ,mass4 ,the ,parlor ,gardener4 ,a ,treatise on the ,house-,culture of ,ornamental ,plants4 ,by ,,cornelia ,j4 ,,randolph4 ,with illustrations4 ,sold by all booksellers1 and sent by mail1 postpaid1 on receipt of price4 ,,lee ,,and ,,shepard ,publishers ,boston 99 99 99 99 99 ,a ,,popular ,,history ,,of ,,our ,,country ,,young ,,folks' ,history of the ,united ,states ,,by ,,thos4 ,,wentworth ,,higginson4 ,square #afmo4 #chj pp4 ,with over #ajj ,illustrations4 ,price #a4ej4 ,the theory of the book can be briefly stated2 it is1 that ,american ,history is in itself one of the most attractive of all subjects1 and can be made interesting to old and young by being presented in a simple1 clear1 and graphic way4 ,in this book only such names and dates are introduced as are necessary to secure a clear and definite thread of connected incident in the mind of the reader2 and the space thus saved is devoted to illustrative traits and incidents1 and the details of daily living4 ,by this means it is believed that much more can be conveyed1 even of the philosophy of history1 than where this is overlaid and hidden by a mass of mere statistics4 ,compact1 clear1 and accurate4444 ,this unpretending little book is the best general history of the ,united ,states we have seen4--,the ,nation4 ,the book is so written that every child old enough to read history at all will understand and like it1 and persons of the fullest information and purest taste will admire it4--,boston ,daily ,advertiser4 ,it is marvelous to note how happily ,mr4 ,higginson1 in securing an amazing compactness by his condensation1 has avoided alike superficiality and dullness4--,boston ,transcript4 ,,lee ,,shepard ,publishers ,boston 99 99 99 99 99 ,,by ,,george ,l4 ,,vose ,a ,,manual ,,for ,,railroad ,,engineers ,,and ,,engineering ,,students #afe ,woodcuts and #ca large ,plates4 ,cloth4 #hvo4 #ab4ej4 ,,the ,,same in two volumes4 ,cloth4 #ae4jj4 ,volumes sold separately3 ,text #f4jj1 ,plates #i4jj4 ,,elementary ,,course ,,of ,,geometrical ,,drawing ,with #ch maps4 ,oblong ,folio4 ,cloth4 ,net1 #e4jj4 ,a ,,sketch ,,of ,,the ,,life ,,and ,,works ,,of ,,george ,w4 ,,whistler1 ,,civil ,,engineer #hvo4 ,cloth4 #a4jj4 ,,bridge ,,disasters ,,in ,,america--,,the ,,cause ,,and ,,the ,,remedy ,handbook size4 ,cloth4 #ej cents4