THE appearance of the second supplement to Watts' “Dictionary of Chemistry” is an event in the history of chemical literature which will certainly be elcomed by all English chemists. Although it may be said with truth that no great generalisations have been made of late years in chemistry, the science is nevertheless advancing with gigantic strides so far as the accumulation of facts is concerned. Perhaps no science possesses such an extensive journalistic literature as Chemistry; month after month the journals of the Chemical Societies of London and Berlin, the Gazzetta Chimica Italiana, the Annalen der Chemie, Poggendorff's Annalen, the Annales de Chemie, the proceedings and transactions of the various learned Societies, as well as numerous smaller chemical publications, all contribute to the vast store of facts already recorded. It is not to be wondered, then, that during the nine years which Mr. Watts devoted to the compilation of his dictionary, the science should have continued its growth at such a pace that the author found it necessary to promise on the completion of the work (Preface to Vol. V., 1869) a supplementary volume bringing the record of discovery down to the existing state of knowledge. The first supplement accordingly appeared in 1872, bringing the history of the science down to the end of 1869. The volume now before us carries the record of discovery down to the end of 1872, and includes some of the more important discoveries made in 1873 and 1874. A Dictionary of Chemistry and the Allied Branches of other Sciences. By Henry Watts, &c. Second Supplement (Longmans, Green, and Co., 1875.)