Mr. Grove on the Gas Voltaic Battery. 271 



The advantage of this form over that which I shall next 

 describe, is the facility with which the tubes are filled with 

 liquid, and the absence of any necessity of touching the elec- 

 trolyte with the fingers. On the other hand, its disadvantages 

 are the difficulty of examining the gases after experiment, and 

 the impossibility of doing so during experiment without chan- 

 ging the electrolyte, as in order to examine the gases the whole 

 apparatus must be immersed in a water-trough, and the cover 

 with the attached tubes taken off" while the jar and the ends 

 of the tube are under water. 



Fig. 4 represents a cell of the Fig. 4. 



second form ; b, c, d, e is a par- 

 allelopiped glass or stoneware 

 vessel, such as is commonly used 

 for the outer cells of the nitric 

 acid batteries ; the tubes are ce- 

 mented into pieces of wood, a b, 

 ac, and can with the wood be 

 separately detached from the 

 trough, as shown in fig. 5. At 

 the aperture or space, a a, be- 

 tween the tubes there is just 

 room for a finger to enter, close 

 the orifice of either tube, and 

 thus detach it from the appa- 

 ratus. In this figure the pla- 

 tinum foil is turned up round 

 the edge of the tube, instead of 

 being attached to a wire sealed into the glass, and instead of 

 a mercury cup there is a binding-screw connexion ; but it is 

 obvious that this part of the arrangement may be interchanged 

 with the other apparatus, or varied ad libitum. This appa- 

 ratus I have found in practice to be very much more conve- 

 nient than the former, from the facility of detaching either 

 tube so as to discharge some of the gas, if it be desirable to 

 alter the level of the water-mark ; or to examine or change the 

 gas in any of the tubes. On the other hand, it has the disad- 

 vantage of requiring the finger to be immersed in the electro- 

 lyte, which, when the latter is of an active chemical character, 

 is unpleasant and in some cases injurious. In fig. 6, a battery 

 of five cells of this construction is represented as when charged 

 with oxygen and hydrogen, and having been for some time 

 connected with the voltameter (fig. 7), the tubes of which are 

 of the same size as those of the battery. 



In the form last described (figs. 4 and 6), the tubes were all 

 as nearly of the same size as could be procured ; they con- 



