286 On the Conslruction of Voltaic Batteries. 



by a space of three fourths of an inch, the bottom being on a 

 level with the lower edge of the holes and soldered to the 

 laro-er cylinder ; this chamber is intended to hold crystals of 

 sulphate of copper when required, and to receive the solution, 

 which should not rise higher than the tipper edges of the 

 holes. A small quantity of the ammoniacal solution is to be 

 poured outside the membrane until it rises to the upper edge of 

 the zinc; the latter solution does not require renewal; the 

 former will require the addition of a few crystals of the sul- 

 phate every four hours. An electro-magnet of the horse-shoe 

 form, the limbs of which were five inches long and one inch 

 in diameter, having four coils of thin wire, each coil contain- 

 ing thirty feet, when connected with a battery of the dimen- 

 sions given, sustained for several hours a weight of 112 lbs.; 

 but this is not a safe test, for I have always observed that 

 electro-magnets to which weights have been for some time at- 

 tached, lose their temporary power to a certain extent, and 

 acquire a slight permanent power. This arises, I apprehend, 

 from the straining of the soft iron and the consequent uneven- 

 ness of the poles, as well as from a certain change in the con- 

 tiguity and internal arrangement of its particles, and presents, 

 in my opinion, an insurmountable obstacle to the nseful appli- 

 cation of electro-magnetic power in the way alluded to by 

 Mr. M'Gauley at the late meeting of the British Association. 



Upon the same principle, conjoined with another which in 

 a future paper I shall more particularly advert to, I have con- 

 structed a somewhat different form of battery for intensity ef- 

 fects ; it consists of a number of zinc and copper cylinders, of 

 the same proportions as those before described, placed in a pot 

 of the same size as that already mentioned, one within the 

 other, the copper cylinders being lined with caoutclwuc for in- 

 sulation. In this battery the power is immense in proportion 

 to the quantity of the metals used, and arises, I conceive, from 

 the application of a principle which I believe is quite novel in 

 the construction of voltaic batteries, namely, that o{ diminish- 

 ing the metallic surfaces as the fluid in its onward passage 

 acc2imidates, thus acquiring increased force in proportion to the 

 smallness of the substance to which it is restricted. By merely 

 altering the connexions of the plates, which by the mode I 

 have adopted can be done with the utmost facility, this battery 

 can be turned into a powerful quantity one, and for both, a 

 wine-glass full of the solutions is amply sufficient. 



In a future paper I hope to be able to enter at greater length 

 into these and other results of the investigations in which I 

 have been for some time engaged. 



Beaufort House, Killarney, FreD. Wm. MulliNS, 



Sept. 1, 1836. 



