143 
Electric Condition of Iron, 
Jail. 1st, 1839. A galvanic combination of iron and zinc 
was put in communication with two poles of a differential 
galvanometer ; a like-sized combination (or gal. pair) of copper 
and zinc was connected with the other two poles of the diff. 
galvanometer : Deviation of needle in favour of the iron and 
zinc pair = 25 degrees. 
Feb. 27j 1839. Experiments made on the comparative 
power of two galvanic batteries fitted up on Wollaston’s 
plan {that is with the negative plate opposed to both surfaces 
of the zinc or positive plate.) The size of the plates was the 
same in both batteries, viz. zinc plate 2J inch, by 2|^ inch. 
The number of pairs in each battery was ten. The only 
difference between the two batteries was, that the negative 
plates in one were of copper and in the other of iron. 
The exciting solution was dilute sulphuric acid, which was 
not renewed during the experiment, but the experiment was 
continued until the acid was exhausted. The power of each 
battery was applied to the decomposition of water, and the gas 
collected was the measure of the power. 
RESULTS. 
Battery of Copper and Zinc, 
The first cubic inch of gas obtained in 33 minutes. 
Then one half cubic inch ... in 92 minutes. 
Acid was now exhausted. H cubic inch in 125 minutes. 
Acid now exhausted. 4 cubic inch, in 104 minutes. 
Iron battery with a measured quantity of acid gave 4 cubic 
inches in 104 minutes. 
Copper battery with a like quantity of acid gave only 1 J 
cubic inch in 125 minutes. 
Battery of Iron and Zinc, 
First cubic inch obtained 
Second — — 
Third — — 
Fourth — — 
in 7 minutes, 
in 9 minutes, 
in 26 minutes, 
in 62 minutes. 
I have the honour to remain. 
Dec. 16, 1839. 
Gentlemen, yours, &c. 
Martyn J. Roberts. 
