724 Transactions oi the American Institute. 



ready for use. It consists of a series of glass cells, each tliree inches 

 long and one inch in diameter, inserted in a wooden block ; a zinc 

 cover is provided for each glass, and a projection from this zinc cover 

 into the irlass forms the zinc element. The other element is carbon, 

 carefully connected with platinum, and well insulated from the zinc 

 cover. A plate of soft rubber is interposed between the zinc cover 

 and the glass top, and the packing is made completely air tight and 

 water tight by the pressure of two rubber straps, extending from the 

 cover to the base board. Connection between each two cells is made 

 by short pieces of spiral springs. The battery is charged by filling 

 tlie glasses half full of water, adding some bisulphate of mercury, 

 and a little shred of cloth is interposed between the plates, so as to 

 retain moisture. When the battery is to be used it is inverted^ 

 thus throwing the fluid into the opposite end of the glass vials, over- 

 flowing the elements and saturating the piece of cloth. On restoring 

 the battery to its proper position, the fluid leaves the plates, Avith the 

 exception of the minute portion retained by the cloth, which, how- 

 ever, is sufiicient to excite j^owerful intensity currents, producing 

 violent muscular contractions, even forty-eight hours after this 

 immersion of the plates. A single drop of fluid being thus eflicient, 

 the constructors believe their battery, once charged, would last a year 

 or more for giving occasional etfects. A modification of this arrange- 

 ment is made by inserting a tube to carry off the gas formed by 

 decomposition, when a fluid of greater energy is used. The battery 

 can be completely renewed at the rate of fifty cells in one hour; and 

 150 cells exceed in intensity 100 cells of the Grove battery. In the 

 arrangement first described, no acid is used, and no gas generated. 

 When great intensity is required this battery will be found less 

 troublesome and more convenient than many of the ordinary 

 foifins. 



Ventilation of Public Buildings. 



In a paper read by Gen. Morin, director of the Imperial Conserva- 

 tory fif Arts and Trades, before a meeting of mechanical engineers, 

 in Paris, the opinion is expressed that the difl'erent arrangements for 

 getting rid of vitiated air and replacing it by fresh air hy means of 

 suction, when well proportioned and well carried out, arc more 

 oflV'ctual vhun those which depend exclusively on blowing iii fresh 

 M'r, a« the latter do not, in every instjince, and at all times, insure 

 fli' viti:»rf'd air bein<; uniformly nnd continuously ex])elled. The 



