Air, and its Relations to Life. By Walter Noel Hartley,
F.C.S. (Longmans, Green, and Co.)—Although scientific books have been issuing from the press in large numbers during the last few years, ranging over all the sciences and of every grade, only one (Dr. Angtis Smith's "Air and Rain ") has been specially devoted to this subject, and this from its costliness is not available for ordinary students. Mr. Hartley, in publishing the substance of his 1874 summer lectures at the Royal Institute, with some additions, has supplied this deficiency, and given us, in addition to the usual matter, the results of the latest investiga- tions. And what is equally valuable and important, he has treated these results historically, tracing the progress of a discovery through the hands of successive experimenters. Thus we have the history of air- analysis from its first beginning, in the laboratory of Lavoisier, to its culmination by Dalton, Dumas, Bonssingault, and Lowy, with a full description of their various methods. The several constituents of air receive separate attention, and are illustrated by various and in some cases new experiments. Pettenkofer's delicate method of determining the quantity of carbonic acid in the air, by neutral- ising a measured quantity of baryta-water, from which a portion of the haute has been withdrawn as barium-carbonate, by a solution of oxalic acid of such strength that a cent. cube is equivalent to a milligramme of carbonic acid, is here given in detail, as well as Dr. Angus Smith's ingenious apparatus, which can be used by any one, how- ever unskilled in volumetric analysis. The principles of ventilation are laid down with a completeness they have never before received, and constitute one of the chief features of the book ; the statistics given of the analysis of air in several public buildings show how utterly they have been misunderstood. The question of heterogenesis, which has been recently revived and warmly discussed by Dr. Bastian, is reviewed in its entirety, and full particulars of the researches of M. Pasteur, Pouchet, and those of the author himself, placed impartially before the reader. We would recommend all interested in this controversy to carefully study the account of these observations, and if after doing so they believe in the principle of archobiosis they have more faith than we can lay claim to.