MR. GROVE ON THE GAS VOLTAIC BATTERY. 
93 
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. Plate V. fig. 1 
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 /As capable of being detached at 
pleasure, in order to introduce a tube for charging the apparatus with gas ; p r, p' r' 
are strips of well-platinized platinum foil, slightly curved like a cheese scoop to keep 
them erect and in the centre of the tube, and rivetted 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 reinversion the tubes may be charged with gas from a crooked tube 
and bladder. The apparatus (fig. 1.) is represented 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 liquid, and the absence of any necessity of touch- 
ing the electrolyte 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 changing 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 second form ; b, c, d, e is a parallelopiped glass or 
stoneware vessel, such as is commonly used for the outer cells of the nitric acid bat- 
teries ; the tubes are cemented into pieces of wood, a b, a c, and can with the wood 
be separately detached from the trough, as shown in fig. 5. At the aperture or space, 
a a , between the tubes there is just room for a finger to enter, close the orifice of 
either tube, and thus detach it from the apparatus. In this figure the platinum 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 apparatus I have found in practice to be very 
much more convenient 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 disadvantage of requiring the finger to be immersed in the electrolyte, 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 
* See Postscript, 
o 2 
