256 



EXPERIMENTAL INVESTIGATIONS, 



philosophers, but I must take the liberty of dissenting from it 

 and of adhering to that which I expressed in my original 

 paper. My grounds of dissent will be seen in some of the 

 ensuing pages. 



In describing the apparatus used in the following ex- 

 periments I shall mention three forms of gas battery, with 

 the first two of which my experiments were all performed ; 

 the latter has only occurred to me while writing -this paper. 

 I have, therefore, not yet had an opportunity of trying it,* 

 but it appears to me by far the best of the three, though, 

 doubtless, superior modifications will shortly be discovered. 



Fig. I. Fig. 2. 



Fig. 3- 



o Ti 



Fig. I, represents one of 

 these forms ; a, b, c, d is 

 a wide-mouthed glass jar, 

 into which a wooden 

 plug, a, b, fits tightly by 

 means of attached pieces 

 of cork ; this wooden 

 cover is perforated to 

 receive the tubes o, h, 

 of which the size is such 

 that the content of h shall be double that of o, and which 

 are firmly cemented into it ; the wooden cover is shown in 

 plan in fig. 2 ; the piece f is capable of being detached at 

 pleasure, in order to introduce a tube for charging the appa- 

 ratus with gas ; p r, p f r' are strips of well-platinised platinum 

 foil, slightly curved like a cheese-scoop to keep them erect 

 and in the centre of the tube, and riveted or welded to stout 

 platinum wires, which are hermetically sealed into the glass, and 

 terminate in brass mercury cups at g, g. This form of battery 

 is charged by inverting it so as to fill the tubes with liquid ; 

 on re-inversion the tubes may be charged with gas from a 

 crooked tube and bladder. The apparatus (fig. I.) is repre- 

 sented as charged and ready for use ; and in fig. 3 is a battery 

 of five cells, also represented as just charged. 



The advantage of this form over that which I shall next 

 describe is the facility with which the tubes are filled with 



* See Postscript. 



