199 



Mr. Walker read a communication, entitled " Observations 

 on Nebulas with a fourteen feet Reflector, by H. L. Smith and 

 E. P. Mason, during the year 1839, by E. P. Mason," which 

 was referred to a Committee. 



Dr. Hare made a verbal communication in reference to the 

 extent at which the galvanic influence could be extended 

 through a coil of wire. 



Dr. Hare stated, that he had prepared a coil of copper wire, No. 

 26, nearly a mile in length, by means of which, and a strap of copper, 

 three inches in width, and 196 feet in length, he had been enabled to 

 repeat the experiment of Professor Henry, for exciting a Faradian 

 current. The wire was covered with cotton, and was coiled upon a 

 wooden sieve hoop. Being suspended over a pulley, and counter- 

 balanced by a weight over the strap, when this was placed in the cir- 

 cuit of a calorimotor, so that the circuit might be broken by drawing 

 one of the electrodes over a rasp or ratchet wheel, communicating 

 with the coil, shocks were felt, when the distance of several feet in- 

 tervened, and they became intolerable when the coil and strap were 

 nearly in contact. Having this coil at command, it occurred to Dr. 

 Hare, to ascertain how far it would be competent to act as a multi- 

 plier. It seemed to be a problem which was yet to be solved, how 

 far the extension of the length of the coils employed would affect 

 their efficacy. He had not heard of any one in which resort had 

 been had to an extension so great as a mile. Actuated by these con- 

 siderations, Dr. Hare supported his coil in a vertical plane, and 

 placed upon the lower and under surface of the hoop, the magnetic 

 needle of an ordinary multiplier. A five cent piece, and a disk of 

 zinc of the same size, being separated by a piece of moistened paper, 

 when one of the ends of the coil was made to touch the silver disk 

 and the other the zinc, the needle moved nearly a quadrant at every 

 contact. When the disk was divided into four parts, every one of 

 them was adequate to produce a movement in the needle, when the 

 coil was made the medium of discharge. That such minute portions 

 of metal should be capable of creating an electrical current in so long 

 a coil, and sufficiently copious to influence a magnetic needle, would 

 have appeared incredible to him, had it not been thus proved experi- 

 mentally. 



Dr. Hare stated the general results of some experiments, 



