Dr. Turner's Elements of Chemistry, 63 



such as may be useful to the student. Dr. Turner has not 

 been very successful in effecting this desideratum, and has 

 unnecessarily introduced two sections, the one on electricity, 

 the other on galvanism. He also talks of the ** science of 

 galvanism," which is in bad taste, and erroneously asserts 

 that the energy of the pile is proportional to the degree of 

 chemical action which takes place ; a statement by no means 

 correct, inasmuch as the energy of De Luc's column is directly 

 proportional tothe number of alternations, andappears entirely 

 independent of chemical action ; and again, a series of 2000 

 plates, arranged in the usual Voltaic apparatus, when per- 

 fectly bright and clean, and the cells filled with distilled 

 water only, give a much more powerful shock, and cause 

 a greater divergence of the leaves of the electrometer than 

 when the apparatus is charged with diluted acids. Here, 

 those very singular phenomena, which electricians distin- 

 guish by the terms quantity and intensity, appear perfectly 

 distinct ; and between these our author does not sufficiently 

 discriminate, but jumbles the whole under the term activity. 

 In describing the chemical energies, too, of the pile, or its 

 decomposing powers, the Doctor entirely overlooks the im- 

 portant andf curious influence of water. He says that acid^ 

 and salts are all decomposed, without exception, one of their 

 elements appearing at one side of the battery, and the other 

 at its opposite extremity ; {i. e. we presume, at its positive 

 and negative poles.) But the fact is, that, excepting where it 

 merely acts as a source of heat, nothing is decomposable by 

 electricity without the intervention of water ; the hydrogen 

 and oxygen of which respectively accompany the elements of 

 the other compounds. Not an atom of potassium can be 

 obtained unless the potassa be moistened ; nor can any salt 

 be decomposed except water be present. Sir Humphry 

 says, it is required, to render the substance a conductor ; 

 but its operation is more recondite, and there is something 

 mysterious and still unexplained in the uniform appearance of 

 hydrogen and oxygen at the opposite poles, when far apart 

 in water, and in all other cases of true polar electro-chemical 

 decomposition. At page 86, the unfortunate protectors of 

 ships' bottoms are introduced — a subject about which the less 

 is said the better ; — ^and, as to electro-magnetism, it is merely 

 mentioned as to its leading phenomena, in the space of three 

 or four pages; nor is anything new suggested upon the 

 ♦' Theory of the Pile," as it is called, which concludes the 

 subject, and which is dismissed in the brief limit of a pag« 

 iMid a half. 



