Proceedings of the Polytechnic Association. 907 



arrangement is called a condenser. It consists of a great number of 

 sheets of tinfoil, separated by oiled silk. Alternated layers of tinfoil 

 are connected with the opposite and negative poles, so that the moment 

 the current is interrupted the electric charge of the battery will flow 

 on this condenser. This gives the additional advantage of uniting 

 this charge with the original current, as the contact is re-established. 

 The shortening of the spark causes the vibration to be more certain, by 

 which the induced secondary current becomes much stronger. This 

 condenser secures a trifling advantage. Its construction was here 

 practically illustrated by taking a condenser of a Tluhmkorf coil-bar. 

 Dr. J. F. Boynton, at this point, asked permission to exhibit an 

 apparatus which illustrated the subject treated by Prof. Vander- 

 weyde. It consisted of a Geissler tube and a bar of vulcanized rubber 

 rotating over it. The bar was made electric by ft'iction, and its simply 

 passing over the tube caused it to become luminous by temporary 

 induction. 



Elevated Railway and Pneumatic Dispatch Combined. 



The remarks made at a previous meeting are here reported. Gen. 

 E. M. Barnum explained in full by diagrams on the black board his 

 plan for conveying passengers and packages and spoke substantially 

 as follows : 



In this age of inventive genius and progressive civilization, we 

 cannot lono- abide bv old and slow svstems. As the stacje coach has 

 given place to the locomotive and the post boy has fled upon the 

 advent of the electric telegraph, so a conviction of the impossibility 

 of our city travel being much longer accommodated upon surface 

 roads is gradually forcing itself upon the minds of the public. 



Various plans for the relief of Broadway by subterranean roads have 

 been submitted, chief among which are the " Central Underground 

 Pailway," chartered at the last session of the State Legislature, and 

 the " Arcade Railway," which, though defeated at that time, will be 

 again brought forward at the present session. Pending the practical 

 realization of the underground ideas, let us see what plans are 

 maturing for other modes of transit, and to what extent we can avail 

 ourselves of other sources and conditions of motion. 



A ready and sure way of relieving Broadway,' and accommodating 

 the far up town and Westchester county residents, would be to make 

 some other avenues of travel and traflic capable of drawing off" a large 

 share of through transit from that great thoroughfare. The form of 



