and on a new Chemico- Mechanical Battery. 317 



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 1 per I 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 



