THE CONQUEST OF TIME AND SPACE 



boilers with thicker shells; the substitution of steel for 

 cast-iron in certain parts of the locomotive, thereby 

 greatly increasing the strength; and finally, the econ- 

 omizing of steam by compounding. 



There is no way of determining the exact amount 

 of increase in the weight of engines during the last dec- 

 ade, but the figures of some of the great manufactur- 

 ing establishments will give a fair idea of this increase 

 in a general way. In one of these establishments the 

 average weight of a locomotive turned out ten years 

 ago was 92,000 pounds for the engine alone, without 

 the tender. At the present time the engines being 

 manufactured by the same firm average 129,000 pounds, 

 an increase of 37,000 pounds, or something over forty 

 per cent. This average weight, however, gives but 

 an inadequate conception of the size of the largest 

 locomotives now being manufactured. The "hundred- 

 ton" engine has become a commonplace. In 1909 a 

 locomotive weighing, with its tenders, 300 tons was 

 manufactured for passenger traffic on the Santa F^ 

 lines. 



In America there seems to be no limit to the sizes 

 that may be reached ; or at least up to the present time 

 this limit has not been attained. In England and sev- 

 eral of the Continental countries a great difficulty has 

 been found to exist in the unHmited size of locomotives, 

 in the fact that the bridges and tunnels of these rail- 

 roads are, almost without exception, so low that any 

 very great vertical increase in the size of the engine is 

 out of the question without reconstructing many miles 

 of bridges and tunnels at an enormous cost. 



[136] 



