1904.] on New Developments in Electric Uailways. 471 



of the part touchiug the couductor proved to be too great, and a 

 further spring was added, so that the contact arm, constructed of 

 brass and aluminium, which is pressed by the spring against the 

 wire, weighs only 600 gr. (1-^- lb. avoirdupois). 



The spring again is carried by a hinged frame, which in its 

 turn is fastened to a vertical axle. 



To counterbalance the influence of the air pressure on all this 

 structure a square board is fixed to the frame on the other side of the 

 vertical axis, and its size is such that the pressure of air on it just 

 balances the air pressure on the other parts of the collector. 



It was therefore possible to adjust the pressure between collector 

 and conductor to remain the same within narrow limits at any speed. 



The official report of the Studiengesellschaft, for the year 1901, 

 points out that the permanent way of the military line between 

 Marienfelde and Zossen was not in a very good condition, but that it 

 was deemed expedient to gain some experience before relaying it in 

 a substantial manner. 



After describing the preliminary tests at the works of the two 

 manufacturing firms, the report gives the official regulations, drawn 

 up by commissioners deputed by the Royal Railway Direction, Berlin, 

 the Royal Government at Potsdam, and the Royal Post Office at 

 Berlin. They fill five printed pages of the report. 



In this year four sets of trials were run : — 



During the first set the generating station supplied current at 

 25 periods, and the motors were connected only long enough to 

 attain a speed of 100 km. per hour. As soon as this speed was 

 reached the current was cut off and the brakes applied. 



During the second set, and with currents of the same periodicity, 

 the cars were run the whole distance at a speed not exceeding 100 km. 

 per hour. 



As soon as these trials had been run, and all the machinery had 

 been found to work smoothly, the third set was commenced, in which 

 the speed was increased to 130 km. 



Up to this speed no serious defects had shown themselves, but 

 when, during the fourth set of trials, the speed was increased still 

 more, the permanent way gave out, and the cars began to sway in a 

 dangerous manner. 



The highest speed during this year was 160 km. per hour, and 

 the conclusions arrived at were that the conductors and collectors 

 had proved quite satisfactory at these speeds, that three-phase motors 

 were suitable for rapid transit, that the brakes were not quite efficient 

 enough, and that the determination of the resistance of the air was 

 not accurate enough. 



The report further mentioned that the permanent way of the 

 military line was not safe for speeds exceeding 120 km. per hour, 

 and that further observations were required to determine the amount 

 of energy supplied by the power station and the durability of all the 

 machinery and apparatus employed. 



