CATALOGUE OF THE MECHANICAL ENGINEERING COLLECTION. 89 



motives should be provided. Tliat was an order wiiich had to be obeyed, and 

 designers proceeded with tlie task of putting into form the modern locomotive. 



The "American " locomotive reached its zenith in 1872. In that year the 

 Baldwin Locomotive Worlds built 422 engines, the average weight in working 

 order having been 64,000 pounds. Most of the engines were of the 4-4 type. 



The favorite 4-4-0 soon reached the limit of its capacity. The grate area 

 limits, the steam producing power of a boiler, and the first attempts to increase 

 the capacity of the American locomotive were directed to increasing the size 

 of the grates. The most popular engines of that type had deep fire boxes 

 passing between the frames, providing a grate about 34 by 72 inches or 17 

 square feet. The intensity of the popular desire to keep that type of locomo- 

 tive in use may be judged by the ingenious efforts made to enlarge the grate 

 area. The first movement was increasing the distance between the driving 

 wheels so that the grates could be lengthened. Side rods as long as nine feet 

 came into use, but the increase of grate that resulted proved a short-lived 

 remedy. Then came the practice of sloping the grate and raising the center 

 line of the boiler. By this means the back of the grate was brought suffi- 

 ciently high to pass over the rear axle, permitting the fire box to extend back 

 an indefinite distance. This permitted the gi'ate to be made as long as it 

 could be fired. Such grates were sometimes made from 9 to 10 feet long, pro- 

 viding an area of about 30 square feet. That kind of fire box was always very 

 unpopular with the enginemen and was wasteful of coal. 



In 1891 William Buchanan, of the New York Central Railroad, cooperating 

 with A. J. Pitkin, manager of the Schenectady Locomotives, brought out an 

 abnormally large 4—4-0 locomotive to haul the heavy express trains. It was 

 numbered 870, had cylinders 19 by 24 inches, driving wheels 78 inches diameter, 

 weighed 120,000 pounds, of which 80,000 pounds were upon the drivers. The 

 fire box, set above the frames, provided grate area which was 96 inches long 

 and 40| inches wide, a total of 27.3 square feet. There were 268 2-inch tubes 

 12 feet long which, with fire-box area, provided 1,851.5 square feet of heating 

 surface. 



That form of engine was largely copied and made heavier, one group having 

 been made with the engine a total weight of 136,000 pounds with 90,000 pounds 

 on the drivers. This was passing the limit, for 22,500 pounds weight pressing 

 the rail beneath each wheel was more than steel rails or steel tires could 

 endure in a fast running locomotive. 



The locomotive of which this model was made by direct measure- 

 ment was still in use in 1907 on the Pennsylvania Eailroad. 



Cat. No. 307,243 U.S.N.M. 



PART III. 



RAILWAY PERMANENT WAY. 



Included in the exhibits of transportation are models of railways, 

 models of rails of various designs and sections of over one hundred 

 types of iron and steel rails used since the beginning of the railway 

 era. The more important of these objects are referred to in the fol- 

 lowing general account of the development of the permanent way, 

 the greater portion of which was prepared a number of years ago by 

 Dr. J. Elfreth Watkins, late curator of the Division of Mechanical 

 Technology. 



