MR. DANIELL ON VOLTAIC COMBINATIONS. 
159 
currents, it must not be overlooked that it may be possible for the whole battery, or 
for a certain number of the series of the battery, to force itself a passage through the 
electrolyte on each side of the copper to the tin, and thus to discharge itself by what 
would appear to be a reversed current through the secondary communication. This 
would be determined by the amount of different resistances in the paths which might 
be open to it. In this way we can account for the different degrees of power in the 
extra current, and for its being able to pass through the voltameter at times and not 
at others. 
The only difficulty in now accounting for the original stoppage of the battery cur- 
rent which I observed, consists in my not having been aware that there was any me- 
tallic communication between the tin and any of the battery connections. I am now 
however convinced that, notwithstanding precautions were taken to avoid this, con- 
tact must have taken place. Indeed the distance between the connecting wires and 
the rim of the tin cover was but small, and the jarring occasioned by placing the 
cover in its place may easily have occasioned sufficient disturbance in the arrange- 
ment. This supposition also sufficiently explains why the stoppage could not inva- 
riably be produced when desired. 
I think that I do not deceive myself in believing that the preceding observations 
may not be without interest and importance to those who are actively engaged in 
advancing by experiment our knowledge of one of the most wonderful and widely- 
diffused agencies with which matter has been endowed. If they should answer no 
higher purpose, they may very probably prevent the application of much labour and 
thought in the explanation of phenomena of a very striking but perplexing nature, 
which are very likely to be observed by those who are working in this field of in- 
quiry, and of which in my own case the preceding pages are a very brief abstract. 
At the same time they afford an exemplification of the advantages of the constant 
battery ; for both the diverted currents and the effects of temperature would have 
been masked and lost in the variable results of the common voltaic combinations. 
The effects of heat upon single voltaic circuits have been ably investigated both by 
M. Marianini* and by Mr. Rogers-^ ; but although both these gentlemen purposed 
to extend their observations to compound circuits, or the battery, they have probably 
been prevented by the cause which I have indicated. It is now, however, apparent 
that in the exact measures of different effects which an invariable current of elec- 
tricity will enable experimentalists to undertake, the variations of atmospheric tem- 
perature even must not be neglected. 
I remain, my dear Faraday, 
Yours very faithfully, 
J. F. Daniell. 
King's College, 
March, 1837. 
* Annales de Chimie, tom. xxxiii. p. 132. 
t Silliman’s Journal, January, 1835, 
