4o8 POPULAR SCIENCE MONTHLY. 



and we must direct our vision in another direction. We know 

 that the newspaper can not serve us, for we seek to kill sensations, 

 and it seeks to live on them. We are bound to turn to some jour- 

 nal or periodical which will publish only what it considers sound 

 science and will eschew sensational science; a journal which, just 

 as the London Times is regarded as the authority on political and 

 economical questions, will be looked up to as an authority on mat- 

 ters of science. 



In order, therefore, to protect the public against scientific bub- 

 bles we must impress upon both men and women the fact that an 

 education in science is desirable, and is becoming more important 

 as the world grows older; but until a scientific education becomes 

 more general, it is important that there should be some scientific 

 oracle of Delphos, and I can not think of any better than a well- 

 managed scientific journal, the editors of which will seek for the 

 best information on scientific questions which interest the financial 

 world. When it is known that such a journal admits to its pages 

 nothing that is sensational, when it is realized that the best spe- 

 cialists contribute to it, surely it will become a saving help in times 

 of trouble. 



WHAT MAKES THE TKOLLEY CAK GO. 



By WILLIAM BAXTER, Jr., C. E. 

 II. 



IF the successful operation of a street-railway car by mechanical 

 power depended wholly upon the ability to produce a motor of 

 sufficient capacity to do the work, the problem would be an easy 

 one to solve, and would have been solved long before the advent 

 of the electric motor. Mere ability to furnish the necessary power, 

 however, is not enough to meet the requirements. As already 

 shown, the mechanism must be light, strong, compact, simple, and 

 so well protected that it can not bo injured except under abnormal 

 conditions. In addition, speed-controlling devices must be pro- 

 vided whereby the velocity may be changed at will and in the short- 

 est possible time, and with as nearly absolute precision as possible. 

 This controlling mechanism must also be so arranged that the direc- 

 tion of motion may be varied with the greatest certainty and as 

 rapidly as may at any time be required. The way in which these 



Note. — The illustrations of railway generator and switchboard were made from photo- 

 graphs kindly furnished by the Westinfrhonse Electric and Manufacturing Company. 



For the photographs of the electric truck and car controller we arc indebted to the 

 courtesy of the General Electric Company. 



