27 MAY 1876, Page 20

Class - Book of Chemistly. By Edward L. Youmans, M.D. (Henry S.

King and Co.)—The text-books on this science are so numerous, that we might despair of finding originality in a new one. We can con- gratulate the author, therefore, on having produced a work original in plan and immensely superior to the generality of elementary works. The first part treats of chemical physics, including what is necessary for the student to know in the physical sciences, and is especially good in the treatment of spectrum analysis. The second part treats of chemical principles, and is the most interesting and valuable part of the work. It is well known that chemistry is just now passing through a transitional state, from a few generalisations on observed facts to an exact science, whose laws are inter-related with physical laws, in which the molecule plays an important part. The newest theories are here given with a simplicity and fullness that will recommend it to all teachers who wish their pupils to gain the most recent and intelligent view of this science. Part III. treats of descriptive chemistry, in which, of course, the facts are old ones, but in arrangement it is superior. All the perissad elements are taken first, subdivided into groups of like affinities, and then the artiads. Organic chemistry forms the last division. The article on fermentation is scarcely up to the latest discoveries, but will doubtless be improved in a fnture edition. Sulphur is not essential to the growth of the yeast-plant.