OF ALL heat engines, the locomotive is probably the least efficient, principally due, no doubt, to the fact that it is subject to enormous radiation losses and to the fact that it must carry its own steam plant. However, even with these serious handicaps, the utility and flexibilty of this self-contained power unit are so great that only in a comparatively few instances have the railroads been able to see their way clear to adopt electric locomotives and, even in these cases, only for relatively small distances.
Stephenson's "Rocket" was in its day considered a wonder and when pulling one car was capable of a speed of probably 25 miles per hour. The fact that our present-day "moguls" can draw a heavy limited train at 80 miles per hour gives some indication of the theoretical and mechanical developments which have made this marvelous advance possible.
In the development of any important device, what seem to us now as little things often have contributed largely to its success-- nay more, have even made that success possible. No locomotive had been at all successful until Stephenson hit upon the idea of "forced draft" by sending the exhaust steam out of the smokestack. This arrangement made possible the excessive heat of the furnace necessary to form steam rapidly enough to satisfy the demand of the locomotive. From that time on the progress made was merely a question of taking advantage of improvements in workmanship and design and later of such valuable principles as compound expansion, valve gearing, etc.
The historical development of the locomotive and the discussion of the theoretical and mechanical improvements, which have made it what it is today, are exceedingly important to the engineer and of great interest to the layman. The practical side of the subject has been exceptionally well handled in this book and will be found profitable to all readers.