July 4, 1902.] 



SCIENCE. 



13 



which the finished structure must fulfill, 

 the design of every detail to cai-ry the 

 stresses due to the various loads imposed, 

 the manufacture of the material compo- 

 sing the bridge, the construction of every 

 member in it, and finally the erection of 

 the bridge in the place where it is to do 

 its duty as an instrument of transportation. 



A close study of the economic problems 

 of transportation in the United States and 

 the experimental application of its results 

 led the railroad managers to the definite 

 conviction that, in order to increase the 

 net earnings while the freight rates were 

 slowly but steadily moving downward, it 

 was necessary to change the method of 

 loading by using larger cars drawn by 

 heavier locomotives, so as to reduce the 

 cost of transportation per train mile. 

 While these studies had been in progress 

 for a number of years and there was a 

 gradual increase in the weight of locomo- 

 tives, it is only within the past five years 

 that the test was made, under favorable 

 conditions and on an adequate scale, to 

 demonstrate the value of a decided advance 

 in the capacity of freight cars and in the 

 weight of locomotives for the transporta- 

 tion of through freight. The test was 

 made on the Pittsburgh, Bessemer and 

 Lake Erie Railroad, which was built and 

 equipped for the transportation of iron ore 

 from Lake Erie to Pittsburgh and of coal 

 in the opposite direction. 



When this economic proposition was 

 fairly established, it was wonderful to see 

 how railroad managers and capitalists met 

 the situation, by investing additional capi- 

 tal for the newer type of equipment, and 

 for the changes in road bed and location 

 necessarily involved by that in the rolling 

 stock. Curves were taken out or dimin- 

 ished, grades were reduced, heavier rails 

 were laid, and new bridges built, so that 

 practically some lines were almost rebuilt. 

 The process is still going on and money 



by the hundred millions is involved in the 

 transformation and equipment of the rail- 

 roads. Some impression of the magnitude 

 of the change in equipment may be gained 

 from the single fact, that one of the lead- 

 ing railroads has within a few years ex- 

 pended more than twenty millions of 

 dollars for new freight cars alone, all of 

 which have a capacity of 100,000 pounds. 

 The form of loading for bridges almost 

 universally specified by the railroads of 

 tins country consists of two consolidation 

 locomotives followed by a uniform train 

 load. These loads are frequently chosen 

 somewhat larger than those that are likely 

 to be actually used for some years in ad- 

 vance, but sometimes the heaviest type of 

 locomotives in use is adopted as the stand- 

 ard loading. The extent to which the 

 specified loadings have changed in eight 

 years may be seen from the following state- 

 ment based on statistics compiled by Ward 

 Baldwin and published in the Railroad 

 Gazette for May 2, 1902. 



Of the railroads whose lengths exceed 

 100 miles, located in the United States, 

 Canada and Mexico, only 2 out of 77 

 specified uniform train loads exceeding 

 4,000 pounds per linear foot of track in 

 1893, while in 1901, only 13 out of 103 

 railroads specified similar loads less than 

 4,000 pounds. In 1893, 37 railroads speci- 

 fied loads of 3,000 pounds and 29 of 4,000 

 pounds, while in 1901, 4,000 pounds was 

 specified by 50, 4,500 pounds by 14, and 

 5,000 pounds by 17 railroads. The max- 

 imum uniform load rose from 4,200 in 

 1893 to 6,600 pounds in 1901. 



In a similar manner in 1893 only 1 rail- 

 road in 75 specified a load on each driving 

 wheel axle exceeding 40,000 pounds, while 

 in 1901 only 13 railroads out of 92 specified 

 less than this load. In 1893 only 21 of the 

 77 railroads specified similar loads ex- 

 ceeding 30,000 pounds. The maximum 

 load on each driving wheel axle rose from 



