56 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
mention this circumstance ; at the same time, we must say that the use of 
chloride of silver for a battery was an independent thought on our part. Dr. 
O’Shaughnessy does not appear to have developed the idea into a workable 
battery, although he stated in his book that it would be of value for local circuits in 
signalling. 
In October, 1875,* * * § we made a communication to the Acad^mie des Sciences of Paris, 
including some photographs of the stratified discharge obtained the 3rd of the 
previous month of August ;f also a further communication to the Royal Society in 
18764 on the length of the spark with 600, 1200, 1800, 2400 rod cells, and subse- 
quently, in May, 1877, a short statement of the relative length of the spark in 
different gases at the ordinary atmospheric pressure. § 
Although we do not pretend to have solved the problem of the cause of strati- 
fication in tubes exhausted to a great extent of the gases they originally contained, 
we venture to think that an account of our experiments will to some extent limit 
the field of future inquiry, and that they may have present interest for the elec- 
trician. 
We propose in the first place to deal with the discharge at ordinary atmospheric 
pressures, and in order that the requisite data for comparison with the results of 
other experimenters may he at hand, we here give the electro-motive force of our 
battery. 
The following value was obtained by balancing a battery of 10 chloride of 
silver rod cells against 1 Latimer Clark standard mercurial cell|| (1'457 volt.). The 
chloride of silver battery was kept continuously working through a high resistance, 
and the standard cell only opposed it when the comparison had to be made. 
The zinc of a battery of 10 rod chloride of silver cells, and the zinc of a Latimer 
Clark cell were connected together and to one end of a resistance of 9270 ohms. 
The silver of the battery of 10 cells was connected to the other end of the resistance 
coils. The mercury of the Clark cell was connected to one terminal of a Thomson 
galvanometer, the other terminal of which was connected to a shifting contact plug. 
It was found that there was no deflection of the galvanometer when this plug was 
inserted at 1275. Consequently 
EMF of 1 A g Cl cell 9270 
s — _ — 0-7971 
EMF of 1 Lat. Clark cell 1275 X 10 “ ’ 
Or, EMF of 1 Ag Cl cell = 07271 X D457 = 1'059 volt. 
* Oomptes Rendus, No. 16, p. 686, and No. 17, p. 746. 1875. 
t A fac-simile of one of these will be given in Part II. 
X Proc. Roy. Soc., vol. xxiv. p. 167. 1876. 
§ Proc. Roy. Soc., vol. xxvi. p. 227. 
|| Phil. Trans., vol. 164, p. 
