MARY E. HILL, _Teacher of Physics, Northfield Seminary, Mass._: I like the truly scientific method and the clearness with which the subject is presented. It seems to me admirably adapted to the grade of work for which it is designed. (_Mar. 5, '88._) JOHN PICKARD, _Prin. of Portsmouth High School, N.H._: I like it exceedingly. It is clear, straightforward, practical, and not too heavy. EZRA BRAINERD, _Pres. and Prof. of Physics, Middlebury College, Vt._: I have looked it over carefully, and regard it as a much better book for high schools than the former work. (_Feb. 6, 1888._) JAMES A. DE BOER, _Prin. of High School, Montpelier, Vt._: I have not only examined, but studied it, and consider it superior as a text-book to any other I have seen. (_Feb. 10, '88._) E. B. ROSA, _Teacher of Physics, English and Classical School, Providence, R.I._: I think it the best thing in that grade published, and intend to use it another year. (_Feb. 23, '88._) G. H. PATTERSON, _Prin. and Prof. of Physics, Berkeley Sch., Providence, R.I._: A very practical book by a practical teacher. (_Feb. 2, 1888._) GEORGE E. BEERS, _Prin. of Evening High School, Bridgeport, Conn._: The more I see of Professor Gage's books, the better I like them. They are popular, and at the same time scientific, plain and simple, full and complete. (_Feb. 18, 1888._) ARTHUR B. CHAFFEE, _Prof. in Franklin College, Ind._: I am very much pleased with the new book. It will suit the average class better than the old edition. W. D. KERLIN, _Supt. of Public Schools, New Castle, Ind._: I find that it is the best adapted to the work which we wish to do in our high school of any book brought to my notice. C. A. BRYANT, _Supt. of Schools, Paris, Tex._: It is just the book for high schools. I shall use it next year. _Introduction to Chemical Science._ By R. P. WILLIAMS, Instructor in Chemistry in the English High School, Boston. 12mo. Cloth. 216 pages. Mailing Price, 90 cents; for introduction, 80 cents; Allowance for old book in exchange, 25 cents. In a word, this is a working chemistry--brief but adequate. Attention is invited to a few special features:-- 1. This book is characterized by directness of treatment, by the selection, so far as possible, of the most interesting and practical matter, and by the omission of what is unessential. 2. Great care has been exercised to combine clearness with accuracy of statement, both of theories and of facts, and to make the explanations both lucid and concise. 3. The three great classes of chemical compounds--acids, bases, and salts--are given more than usual prominence, and the arrangement and treatment of the subject-matter relating to them is believed to be a feature of special merit.