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Having had some acquaintance with telegraphing and telegraphers, I desire to call your attention to a point of practice, in the use of the battery, and its explanation by science. Some telegraphers (I know not how many) have laid aside Grove's battery and substituted a modification of Daniell's, asserting, after considerable experience, that it is cheaper —they have rejected the use of the mercury) and the sulphuric acid ; they say that the former is useless—a dead loss—while the latter, in any quantity, eats up the zincs. They place a cylinder of sheet copper in a glazed earthen jar, within this a porous cup, and still within this a Grove's zinc, unamalgamated. The jar is poured two-thirds or three-fourths full of water, and more than enough to saturate it, is added, of sulph. copper. The porous cup is rilled to a level with the fluid outside, simply with water. Now, a person who had taken his ideas of a battery solely from scientific works, would not suppose this would 'go off;' but it does, and practice has demonstrated that it is far superior in length and constancy of action to that in which mercury and sulphuric acid are used—showing, beyond the possibility of a doubt, that they are not only not needed, but positively injurious. Now what is the chemistry of this battery? In consequence of the conjugal union of the copper and zinc in the fluids of the battery, there is developed a force producing constantly a disruption of previously existing affinities. This force is emphatically a "disorgan-izer:" it absolves the oxygen and hydrogen in the porous cup, from their marital vows, and a divorce at once takes place—an atom of oxygen unites with an atom of zinc, leaving the atom ot hydrogen to seek a more congenial element. Disregarding all natural barriers, she traverses the walls of the porous cup, and instantly unites with an atom of oxygen already divorced from the sulphate of copper, leaving the copper uncombined adhering to the copper cylinder. Here all electrical ac-traverses the porous cup traverses the porous wbich the freed sulphuric acid has for the oxyde ot zinc. But a strong affinity does exist here, and an instantaneous combination is effected in the porous cup. Or, on the simpler binary theory." the sulphatoxide of copper, S.O4. Cu., is decomposed, pure copper is deposited on the copper electrode, while the sul-phatoxygen (S.O4.) traverses the porous cup, and unites with the zinc, forming sulphatox-yde of zinc, (S.O4., Zn.) I have described but one series of changes—they succeed one another continually while the battery is in action. There being no superfluous acid in contact with the zinc cylinder, there is and can be no cross-play of affinities, as in the usual form of battery, producing ' local action.' If the impurities are active at all they must produce a circuit in the same direction as the zinc. It seems to me this very battery, got up by practical men—telegraphers—at once illustrates and proves, in a beautiful and forcible manner, Faraday's law of " definite electro-chemical action." For every nine grains of water decomposed, there are eight grains of oxygen eliminated to combine with thi:ty-three of zinc ; one grain of hydrogen, to combine with eight grains of oxygen of oxyde of sulphate of copper; forty of sulphuric acid (real), with forty-one of oxyde of zinc, and thirty-two grains of pure copper deposited. Nothing is wanting and nothing is left. The de-composition and re-composition are complete, and the forces are equal. The iron, as impurity in the zinc, has no sulphuric acid to combine with it, unless it decomposes an atom of water ; in which case sulphate of copper is decomposed, and the acid is obtained from the copper side of the battery, and the current of electricity generated travels the common highway. The cost of an equivalent of quantity, generated by this battery, taking Mathiot's data (Sci. Am., Vol. 6, page 43), is about 87; ard of power with which telegraphers have principally to do, 43 or 44. But when we take into the account the fact that this battery will hold good for a month without renewing, merely adding water and blue vitriol . from time to time, while, on the other hand, i the Grove's—well amalgamated—only for a few days, together with the fact that in the hands ot operators, generally there is not that scientific precision requisite for the economical working of so complicated a battery—the zincs imperfectly amalgamated or not at all— the quicksilver wasted, and the refuse amalgam thrown away—no one will be disposed to question the cheapness of this telegraph battery. I think the mechanical arrangement of this battery may be very materially improved, and I intend to devoted some study and experiment to it soon. In the description of Farmer's battery, in your paper, reference was made to a certain law laid down by Ohm, which I am very anxious to see elucidated and illustrated. It may not be new, but that is the only time I recollect to have seen any reference to it. *. *. *. Ottawa, 111., July 11, 1853.
