154 
ME. DANIELL ON VOLTAIC COMBINATIONS. 
Voltameter alone .... 5 cubic inches per five minutes. 
Voltameter with galvanometer 4 cubic inches per-five minutes. 
At this temperature there was no current from the tin by either connection. 
When the steam was turned on, the battery current increased rapidly to 85° E. by 
the galvanometer, and there was a current from the tin connections notwithstanding 
the glass insulation. This extra current was also found to exist during the flow of the 
main battery current ; and when the two were measured by separate galvanometers, 
The battery current was . . . 85° E. 
And the extra current .... 30 E. 
It again made no difference whether the tin took the place of the zinc or the cop- 
per in the arrangement ; the deflection was always in the same direction. 
The breaking of neither current affected the other. 
To ascertain whether heat alone, independent of the steam, was the cause of this 
extra current, a tin plate was placed upon the hot sand of a sand-bath, and the bat- 
tery cells transferred to glass plates upon it. At first no extra current was detected ; 
but as the temperature rose to 150° and 200°, the second galvanometer was affected 
to the amount of 50° or 60° ; and this whether the battery circuit was complete or 
not. A deflection was even occasioned by making the contact with any part of the 
iron stove, however distant, with which the tin plate was in contact. 
These experiments were repeated and varied numberless times, but not with uniform 
results : sometimes the extra current had sufficient intensity to pass through a volta- 
meter, producing slow decomposition of the water ; but most frequently, however great 
the deflection of the needle, it would not pass through this obstacle. At other times, 
in apparently similar circumstances, the extra current could not be detected at all. 
Whenever produced, however, it was always observed to flow from the tin to the bat- 
tery, whether the connection with the latter were made with the zinc or the copper, 
I now placed one of the battery cells upon a piece of wood in an iron case made 
to receive it, of the same height, but having a space all round it of about an inch. 
When the primary circuit was completed by means of a galvanometer, the deflection 
was 60° E. ; but there was no action upon a second galvanometer included in a 
secondary circuit between the iron and the zinc or the iron, and the copper of the 
cell. A little dilute sulphuric acid was then poured into the iron case, and imme- 
diately a strong extra current was produced. Under these circumstances 
The primary current was 60° E. 
The extra current copper and iron connection . . 20 E. 
Zinc and iron 40 E. 
The analysis of the phenomena of these extra currents was most satisfactorily per- 
formed in the following manner : — in figg. 5, 6, and 7? let i i i i represent the section 
of the iron case, c c c c the section of the copper cell, and z z the zinc rod : let G also 
represent the situation of the secondary galvanometer with its different connections 
with the circuit. In fig. 5. the connection with the iron is made with the copper cup 
of the galvanometer, and the zinc cup is connected with the copper of the cell ; and 
