Page:Science vol. 5.djvu/155

 tUe student with the means of following up the literature of any subject as thoroughly ns he may be iDcUucd. The figures are numerous, uew, and admirably fitted to illustrate the points for which ibey are intended. Altogether, the book is well suited for the wants of beginners, to whom the size and abstmseneas of the larger works on petrography- are often diswjuraging ; and it will doubi1es» Hud many readers in this country as well as in Europe. It would aliuiidantly repay translating inter English.

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��ItMON'S MANUAL UF CHEMISTRY.

��lis book, as the preface inforuis us, is in- indeti as a guide to lectures and laboratory work for lieginners in chemistry, being espe- wally adajited for the use of pharmaceutical and medical students. It is hard to sec, how- ever, in what respects pharmaceutical or medi- cal students need special methods of trt'atment in llieir commencement of ihe study of chem- istry Ijefore they enter upon a study of those particular branches of the science especially necessary to them In their profession.

A iwculiar feature of the book is llie pres- ence of seven colored plates, showing the va- riously shaded colors of the more common chemicals, and their color- rea ctio ns ; such as the red of mercuric iodide, the jellow of arse- nions sulphide, the shades of color produced by the action of reducing-agcnts on a solution of potassium diohromale, etc., ^a feature which can possess little value to a laboratory student, wlio mnst necessarily become familiar with these colored sulwtances and their reactions by personal experience. The liook, however, l>ears Iha appearance of l.wing intended for students who are to have but little laboratory work : and. indeed, with the exception of the IKJriioo treating of metals and their combina- tions, it cannot Ijc considered as a really good text-book for laboratory use.

There is noticeable, moreover, throughout the book, an apparent tack of connection be- tween fact and theory. The facts are given, hut the theory is lacking. When supplemented by lectures, this defect might not be so notice- able. It is, however, a iwint to which the student's attention needs to be constantly called. Chemistry is more than a collection of fatrts : it is a livii-g science. Facts serve as a basis upon which Co build theories; and the mutual connection of fact and theory needs to be constantly indicated, as well as the meth-

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The book, however, possesses some admira- ble features. As a wholtt. it is well written, is systematic, and cont.nins much thai is valuable. Its main defect as an elementary text-liook consists in the attempt to cover too great a varietj- of subjects at the cxi>ense of thorough- ness. Critical examination, moreover, reveals here and there an occasional incorrect or mU- lending statement. Thus, on p. iUiS we ar« told that '■ ptyalin, the active principle of saliva, is a ferment which has the |>ower of con- verting starch into glucose," whereas it has been known for the last five years that the main product of the amylolylio action of saliva is maltose. The method for the determination of nitrogen, given on p. 241, can hardly bo considered as the method generally- used for this purpose, as is claimed by the author ; neither can the method, given on the same page, for the determination of carbon and hy- drogen " by passing dry oxygen gas over the substance heated in a glass tul>c," Ik taken as a satisfactory statement of tlie method gener- ally used for making a ' combustion ' in oxy- gen gas. Again : we are told on p. 359 that I>epsin. in the presence of free hydrochloric acid, does not prevent the continued action of saliva on starch, whereas it has been plainly demonstrated within the last three years that the ferment of saliva is completely destroyed bj- gastric juice, and even by dilute hydro- chloric acid alone.

��i\EW TEXT-BOOKS OF PHYSICS.

Mu- Gagh: states his aim to be. ''to collate in this volume something of value to every teacher of physical science." The book Is divided into five parts : laboratory exercises, manual of manipulation, general review of physics, test-(jnestions. and key to solution of problems. The experiments given in the first part are mostly well enough, and some of them even of considerable ingenuity. They are, however, numbered in a minute fashion, which is likely to mislead one who reads in the announcement that there are two hundred and thirty-eight experiments. Jn the fortj'- live pages devoted to the ' manual of manipit- lalion,' very few directions for manipulation

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