NOVEMBEE 9, 1900.] 



SCIENCE. 



723 



of the educational course so that the student 

 should not be forced to master antiquated ways 

 of looking at things, only to discard them later. 

 While it was necessary in doing this to remodel 

 the conventional type of test-book, as much as 

 possible of the time-honored form of presenta- 

 tion has been kept. * * * 



"One might perhaps teach chemistry as a 

 deductive science, starting from a few general 

 principles and introducing the properties of the 

 different substances as illustrations of the gen- 

 eral laws. This plan has not been followed, 

 partly from an interest in the historical devel- 

 opment and partly from a feeling that there 

 were too many important details to make such 

 a method satisfactory pedagogically. I have 

 therefore kept the traditional arrangement ac- 

 cording to elements and compounds, and have 

 worked in the general laws as best I could. * * * 



" Special pains have been taken with the de- 

 velopment of the conception of ions. Suflicient 

 attention has, perhaps, not been paid to the 

 fact that it is possible and necessary to intro- 

 duce this conception as a purely chemical and 

 not as an electrical one. Although this idea 

 was actually developed to explain the electrical 

 phenomena, its importance in chemistry lies in 

 its accounting for the chemical facts of reactions, 

 characteristic of the constituents of salts. This 

 is the point upon which stress has been laid. 

 The electrolytic phenomena and Faraday's law 

 serve, then, to widen and deepen the concep- 

 tion already deduced from the chemical phe- 

 nomena." 



The first three chapters form an introduction 

 in which we find a brief but very lucid exposi- 

 tion of our fundamental concepts in regard to 

 matter ; a statement of the facts from which we 

 deduce the laws of the conservation of mass 

 and of energy ; a discussion of combustion phe- 

 nomena, with special reference to the changes 

 of weight involved, and to the dissociation of 

 mercuric oxide. The epistemological stand- 

 point taken in the first chapter is very much 

 more satisfactory than the materialistic one 

 usually adopted. It is difficult to see any ped- 

 agogical advantage in postulating ' matter, ' 

 and it is certainly better, from a scientific 

 point of view, to state what we know than to 

 start with an assumption, however plausible. 



The besetting sin of most chemists is to 'substi- 

 tute hypotheses and analogies for facts, and to 

 believe that an analogy is an identity. The 

 chemist is very ready to reason that, since 

 Brown acts like Jones under certain cii'cum- 

 stances, Brown must therefore be Jones. 



In the fourth chapter, Ostwald gives a brief 

 sketch of the different elements, and is then 

 able to refer to any element at any time as a 

 substance with which the student is already 

 familiar. Probably every chemist has tried his 

 hand at an arrangement of the subject which 

 should require no use of, nor reference to, any- 

 thing unknown, except the one point or sub- 

 stance under discussion. The difficulties in the 

 way of such a task are enormous, and it is by 

 no means certain that the problem can be 

 solved without sacrificing other points of vastly 

 more importance. The method followed by 

 Ostwald, and before him by Bunsen, eliminates 

 these difficulties and leaves one free to treat the 

 subject in any desired way. It is a method to 

 be defended along other lines. The student 

 has a speaking acquaintance, at any rate, with 

 zinc, iron, lead, mercury, silver, gold and other 

 elements before he begins the study of chemis- 

 try. If this previous knowledge is not to be 

 ignored, there is no reason why it should not 

 be extended in an equally superficial way to 

 include all the other elements. 



The chemistry proper is divided into two 

 parts, the non-metallic elements and the metals. 

 Successive chapters are devoted to oxygen, hy- 

 drogen, water, hydrogen peroxide, chlorine, 

 the oxygen compounds of chlorine, the remain- 

 ing three halogens, sulphur and its compounds, 

 selenium and tellurium, nitrogen, phosphorus, 

 carbon, silicon, boron, and the gases argon, 

 helium, etc. Under the metals, the order is: 

 potassium, sodium, rubidium etc., calcium, 

 magnesium, strontium etc., aluminum and the 

 rare earths, iron, manganese, chromium, cobalt 

 and nickel, zinc and cadmium, copper, lead, 

 mercury, silver, tellurium, bismuth, antimony, 

 arsenic, vanadium etc., tin and the allied 

 metals, uranium etc., gold and the platinum 

 metals. The book closes with a chapter on the 

 choice of combining weights and on the periodic 

 law. 



The treatment is excellent throughout. In 



