317 
and on a new Chemico- Mechanical Battery. 
a battery of feeble force few layers of paper could be inter- 
posed ; but with one of greater strength, forty or sixty thick- 
nesses might be used. A similar form of apparatus might 
easily be devised, which would show by means of a delicate 
screw the exact distance at which a given weight would be 
supported by the attractive force of the induced magnet. 
The influence of different conditions of surfaces is a subject 
which has escaped all experimenters. Now this is singular, 
for many must have noticed, that in a circuit, the greatest 
quantity of gas is given off* at the corners, edges, and points. 
Following this hint, a piece of spongy platinum, consisting as 
it does of an infinity of points, was placed in contact with 
amalgamated zinc, when a most violent action ensued, so that 
but little doubt could be entertained of its forming a very 
powerful battery. The fragile nature of this material pre- 
cludes it from being thus used, and therefore it was deter- 
mined that another piece of platinum should be coated with 
the finely-divided metal. This experiment was attended with 
a similar good result, and the energy of the metal thus coated 
was found to be surprising. To test the value of this process, 
a piece of platinum, thus platinized, was placed in dilute acid 
in contact with amalgamated zinc, and the quantity of gas 
evolved in a given time was noticed. 
c.i. 
Platinized platinum 7 sq. inches gave off 5 per 1 minute 
Platinum heated ditto I per 1 minute 
Platinum covered by air ditto 1 per 6 minutes 
Platinized coke small piece 3 per 5 minutes 
Plain coke ditto 1 per 25 minutes. 
In these experiments the contact was made in each cell alike; 
the same zinc being used, and the distance being the same 
between the metals. The energy of the metal thus prepared 
upon the soft iron magnet is very great. A piece of platinum 
exposing thirty-two square inches of surface, supports three- 
quarters of a pound through seventeen thicknesses of paper, 
whilst when smooth and wetted it supported it through eleven 
layers ; and when no care was taken about its being wet, but 
when simply plunged into the liquid, only through five layers 
of the same paper. 
The cause of this increase of power appears to be the faci- 
lity given to the evolution of the gas from the number of 
points, and not from an increase of surface, as but little benefit 
attends its application in the nitric acid batteries, in which the 
hydrogen is not evolved, but absorbed by the fluid. 
The next point which we have to consider, is whether other 
finely-divided metals have the same good effect ; but no other 
