40 BULLETIN OP THE 



the impression becoming visible when breathed upon. Silver 

 appears to produce the best impressions, nickel the next, copper 

 the least. No other metals appear to have been tried. The im- 

 pressions were generally positive, but a few cases of negative 

 impressions are described. 



Mr. Henry referred to similar experiments made by Mosher 

 many years ago. 



Mr, Henry made a communication 



ON ELECTRICITY ENGENDERED BY THE DRIVING BELT OF THE 

 machinery for VENTILATING THE CAPITOL AT WASHINGTON, 



referring particularly to leather belts, and ascribing the electricity 

 to compression and tension, instead of friction. Large quantity 

 of electricity, with small intensity, is produced. Protection 

 against fire from it in cotton factories was effected by interposing 

 screens of glass. At the Capitol, in Washington, the electricity 

 was utilized for medical purposes by arranging points and con- 

 ductors, so as to collect it, and had been effectively applied in 

 cases of nervous diseases. He found the electricity produced by 

 the belt was negative. 



He also made remarks on the method of lighting gas burners, 

 by what was by some considered the electricity of the body, but 

 which was simply the result of the friction of the shoes on the 

 carpet. The phenomenon had become more common since the 

 introduction of heated air from furnaces into our dwellings. 



Mr. Parker referred to several cases where sufferers had 

 obtained great relief from the application of electricity at the 

 Capitol, 



86th Meeting. April 10, 1875. 



The President in the Chair. 



Forty-eight members and visitors present. 



The President announced the election of Dr. Robert Fletcher, 

 Lieut. Francis V. Greene, U. S. Eng'rs, Prof. Alma H. Thomp- 

 son, and Hon. Samuel Shellabarglr as members of the Society. 



