332 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



Fig 391- the edge of the outer cop- 



per cylinder ; there is a 

 cap with a binding screw 

 on the copper, and also on 

 the zinc, which form the 

 poles, that at the zinc be- 

 ing negative, and the one 

 at the copper being posi- 

 tive. The liquid employed 

 is a solution of blue vitriol, 

 (sulphate of copper) in 

 water, about two ounces 

 lo a quart of water. The 

 liquid requires to be re- 

 newed when the acid is 

 entirely taken up by the 

 zinc, which will be known 

 by there being no deposit 



on the zinc, after being immersed for some time. The zinc 

 cylinder should be left in the solution only while in use, as 

 it soon becomes coated with a deposit, which, after used for 

 an hour or two, should be scraped oif with an old knife, as 

 a clean surface of zinc is requisite to the proper action of 

 the battery. The solution may remain in the copper vessel 

 any length of time, us it does not act on it. There is no 

 unpleasant smell from the use of this battery, and the acid 

 will not injure if spilt on furniture or clothing. 



A battery five and a half inches high, and five inches 

 diameter, is of sufficient power for most experiments in 

 electro-magnetism, for which this battery is best adapted ; 

 where more power is required two or more may be united 

 and used together. Price, - $2.50. 



" smaller sizes, $1.75 and $1.50. 



Fig. 392. 



DanieWs Single Cell Sustaining Battery. 

 (Fig. 329.) This instrument consists of a cylinder 

 of copper, with a bottom of the same metal, con- 

 taining a cup formed of unglazed porcelain, which 

 has a solid rod or cylinder of well amalgamated 

 zinc, supported in its centre. The cylinder is fur- 

 nished with a perforated shelf, upon which a 

 supply of crystals of sulphate of copper are 

 placed ; so that the battery being once charged, 



