and on a new CJiemico-Mechanical Battery, 319 



placed in water, to which a little dilute sulphuric acid and ni- 

 tro-muriate of platinum is to be added. A simple current is 

 then to be formed by zinc placed in a porous tube with dilute 

 acid ; when, after the lapse of a short time, the metal will be 

 coated with a fine black powder of metallic platinum. The 

 trouble of this operation is most trifling ; only requiring a lit- 

 tle time after the arrangement of the apparatus, which takes 

 even less than the description. The cost I find to be about 

 Qd. a plate of 4 inches each way, or 32 square inches of sur- 

 face. This finely-divided platinum does not adhere firmly to 

 very smooth metals, but when they are rough is very lasting, 

 and sticks so closely that it cannot be rubbed off. On this ac- 

 count, when either silver is employed, or copper coated with 

 silver, the surface is to be made rough by brushing it over with 

 a little strong nitric acid, which gives it instantly a frosted ap- 

 pearance, and this, after being washed, is ready for the pla- 

 tinizing process. 



With regard to the arrangement of the metal thus pre- 

 pared great diversity exists ; it may be arranged in the same 

 way as an ordinary Wollaston's battery with advantage ; a 

 battery thus constructed possessing greater power than Pro- 

 fessor Daniell's battery : four cells, containing 48 square 

 inches in each cell, decomposed 7 cubic inches of mixed gas 

 per five minutes, whilst four cells of Professor Daniell's, in 

 which 65 square inches of copper were exposed in each cell, 

 gave off only five cubic inches in the same time. However, in 

 my battery thus arranged, the action dropped to 5 cubic inches 

 in five minutes, but it resumed its power after the contact had 

 been broken for a few seconds. This battery also possesses 

 great heating powers, raising the temperature of a platinum or 

 steel wire, 1 foot long and of a thickness similar to that used 

 for ordinary birdcages, to a heat that could not be borne by 

 the finger"''. Its magnetic power is not less astonishing, three 

 cells supporting the keeper of a magnet through forty-five, 

 two cells through thirty-two, and one cell through twenty 

 thicknesses of paper. An electro-magnetic engine was made to 

 rotate with great velocity, the combustion of the mercury at 

 the breaking of contact being exceedingly brilliant. 



A battery of this construction should be in every laboratory, 

 to be used in most cases where a battery is wanted, and the 

 slight labour attending its operation is scarcely worth men- 

 tioning. I have used one for 48 hours consecutively without 

 the slightest alteration either of the fluid, or in the arrange- 



* A small pot battery of six cells fairly fused into globules 2 inches of 

 iron wire, and the combustion of different metals was extremely brilliant, 

 when the battery was in combination with a BachofFner's apparatus. 



