Mnj' 30, 1872] 



NATURE 



79 



HINRICHS' CHEMISTRY 



The Elimcuts of Chemistry and Miiicraloi^y, by Gus- 

 tavus Hinrichs, A.M. (Griggs, Watson, and Day, Daven- 

 port, Iowa, U.S.) 



THIS is the second volume of Prof. Hinrichs' series 

 of science instruction for schools. In the former 

 volume the elements of Physics were given ; this volume 

 contains the elements of Heat, Chemistry, and Mineralogy, 

 and will be followed by a third, called the " Students' 

 Cosmos." The author has thrown himself entirely into 

 the practical method of teaching the physical sciences — 

 the student has first to perform an experiment, and then 

 draw his own deductions from it. In chemistry, perhaps, 

 more than in the other sciences, this system leads to the 

 best results ; for on all sides laboratory practice is recog- 

 nised as essential to its true understanding. If, however, 

 large laboratories and costly apparatus are required, its 

 introduction in our schools cannot become universal. 

 The author has, however, shown in this volume that by 

 excluding special branches, a considerable knowledge of 

 the elementary methods of laboratory practice may be 

 furnished, almost free of charge, by any school to all its 

 pupils. At a time when science instruction in our schools 

 is attracting so much attention, a series of volumes like 

 the present is peculiarly valuable, and thanks are due to 

 Prof. Hinrichs for his bold effort to show how the physical 

 sciences should be taught. 



The subject " Heat" occupies two chapters. The first 

 deals with the sources of heat, modes of heating, radia- 

 tion and induction, thermometry, calorimctry, and fusing 

 and boiling ; the second treats of the relation of heat to 

 mechanical work. These are extremely clear and practi- 

 cal ; we think better than those which follow. The third 

 chapter is on " Dissociation and Electrolysis." After a 

 few examples of the splitting up of compounds into 

 their elements have been studied, the student is led 

 naturally to the definitions of elementary bodies, of 

 compounds, and mixtures. The next chapter is con- 

 fined to the elements and compounds, and some of 

 the principles of chemical nomenclature ; to this chapter 

 we must certainly take exception, the author has intro- 

 duced a novel and arbitrary classification of the elements, 

 which, we think, will tend to confuse the student. He 

 groups the elements into nine genera, giving the character- 

 istic properties of each : thus we have the kaloids, analo- 

 gousto potassium ; calcoids,analogoustocalcium ; cuproids 

 to copper, and so on ; under the last head we find classed, 

 copper, silver, gold. We cannot see any reasons for such 

 grouping, for neither in their chemical nor in their physi- 

 cal properties do these three elements correspond. 



The author divides chemical substances into monaries, 

 binaries, ternaries, and serials ; the monaries are the 

 elements themselves, the binaries the compounds of two 

 elements, the ternaries of three, whilst the serials com- 

 prise organic bodies ; there is, however, no reason in the 

 author's definitions why the greater number of the serials 

 should not be classed under the ternaries. The term 

 " serials" the author has taken from the fact that numerous 

 organic compounds can be classed together to form series 

 of substances, differing from each other by a definite in- 

 crement. The next chapter treats of the synthesis of 

 acids and bases, and chapter 6 is devoted to chemical 



processes. Under the head of "substitution," the quanti- 

 tative relations of the elements to each other are brought 

 out. We do not think, however, that the difference between 

 the terms "atomic weight" and "equivalent" is by any means 

 sufficiently defined. A considerable space is devoted to 

 the phenomena of double decomposition and to the com- 

 plex processes, such as fermentation, &c., which concludes 

 the chemical portion of the work. A chapter on mineralogy 

 follows, but on this it will be difficult to give an opinion, 

 as the method the author uses is novel, but, according to 

 his account, quite satisfactory. The book on the whole 

 is most carefully written, so that the student cannot fail 

 in his experiments provided he follows his instructions ; 

 these also are so given as to lead to economical and precise 

 methods of working. At the end of the book a number 

 of blank pages are left for the pupil to fill up with his 

 notes of experimencs performed, and results obtained, 

 forming quite a new feature in this class of works. 

 The chapter on the " Chemical School Laboratory " we 

 should recommend to the notice of our teachers, as it 

 gives a description of the author's system of teaching, 

 which, we believe, has succeeded extremely satisfactorily 

 in the case of physics, and, we trust, will be equally suc- 

 cessful in chemistry. 



OUR BOOK SHELF 



Tlic Figure of the Earth, By Archdeacon Pratt. 

 (4th Edition, London: Macmillan and Co.) 



This is the fourth edition of a well-known book, of 

 which we shall unfortunately not now have any more 

 new editions from the hand of its lamented author. 

 The book has grown much since its first edition as a 

 separate work in i860. The chapter on the attraction of 

 table lands, mountains, oceans, &c., has been much 

 enlarged since the first edition, and also the chapter on 

 the determination of the figure of the earth by geodetic 

 operations. A chapter, most valuable to the student of 

 physical mathematics, is inserted on the determination of 

 the ellipticity of the earth (considered as a body whose 

 surface is one of its own equipotential surfaces) from 

 pendulum experiments, the moon's motion, and the pre- 

 cession of the equinoxes, respectively. The student of 

 this subject must carefully bear in mind that no observa- 

 tions taken exterior to the surface of the earth can throw 

 any light whatsoever on the internal arrangement of its 

 matter, inasmuch as, according to the well-known 

 theorems of Gauss, there are an infinite number of ways 

 in which that matter might be conceived as being ar- 

 ranged so as to produce the same external effect. The 

 observations above noticed, however, are calculated to 

 throw light on the question as to whether the surface may, 

 within the limits of approximation, be considered as a 

 surface of equilibrium. 



In fact, it is known that in any event the external effect 

 of the earth may be precisely effected by the distribution 

 in a concentrated form of the whole matter of its interior 

 over its surface. 



The important proposition that any function, which 

 does not become infinite within the limits considered, 

 can be expanded in a scries of Laplace's funclions, is 

 proved by Mr. Pratt in the text by rather a long method, 

 in order to get over a certain apparent objection as to 

 discontinuity. The following proof of that proposition 

 seems short, and not open to objection. 



Let A and B be two points on a sphere of centre O. 

 Let the co-ordinates of any point R referred to A be / and 

 q, where p is the cosine of the angle between R and O A, 



