512 SCIENCE PROGRESS 



Then we have a chapter on the orbits of comets, in which these are explained 

 in as simple language as the case permits ; and, indeed, any one with an ele- 

 mentary knowledge of trigonometry should be able to follow the explanations. 



The chapter on the spectroscopic study of comets, contributed by Messrs. 

 E. W. Maunder and W. E. Rolston, deals fully with the methods and results, 

 from the early visual observations to the recent introduction of the prismatic 

 camera, which shows in such a convenient manner the chemical constitution of 

 various parts of the comet. We quote the following paragraph : 



" We must be content to look on the comet spectrum as radiation, probably 

 produced by electrical action of some kind, from the particles of the comet itself. 

 That the volatile gases of the carbon compounds should be the first to be excluded 

 is not a matter of wonder, whilst the observation that when the comets attain to 

 lesser distances from the sun, and therefore become more strongly heated both 

 by the solar radiation and by the increased number of collisions among their 

 own particles, sodium and iron are vaporised and rendered incandescent, is but 

 another step in accordance with the law of continuity." 



The relation of comets to meteors is discussed, and a chapter on comets in 

 history and poetry will appeal to many readers. 



Among several useful appendices is one in which the catalogue of comets in 

 the author's Handbook is brought up to date, including the faint comet discovered 

 by Borelly in June, 1909. 



The Fundamental Principles of Chemistry. An Introduction to all Text-books 

 of Chemistry. By Wilhelm Ostwald. Authorised Translation by 

 Harry W. Morse. [Pp. xii + 349.] (London : Longmans, Green & Co., 

 1909. Price 7 s. 6d. net.) 



Prof. Ostwald, in his latest volume, has turned his attention to the "Fundamental 

 Principles of Chemistry," and has sought "to work out a chemistry in the form of 

 a rational scientific system without bringing in the properties of individual sub- 

 stances." He describes the work in a sub-title as "An Introduction to all 

 Text-books of Chemistry," but qualifies this in a preface, by adding that he does 

 " not mean that the beginner should absorb the entire contents of this book before 

 he learns about oxygen and chlorine as chemical individuals." He is quite of the 

 opinion that a close personal acquaintance with a considerable number of important 

 and characteristic substances is, and always must be, the fundament of all instruction 

 in chemistry. But when this acquaintanceship has once been obtained, it can be 

 nothing but an advantage to the student to point out to him the great connections 

 by which these separate facts are bound together into a unit. This qualification 

 reflects accurately the character of the book. It is emphatically not a book for the 

 elementary student, and could only be recommended with advantage as a real 

 introduction to the science in the case of a scholar (if such there be) who had 

 mastered the allied subject of physics and wished at a mature age to enter upon 

 the study of the sister science. Only for such a type of beginner would the earlier 

 paragraphs and definitions possess a real and useful significance. 



The method of treatment adopted has certain obvious limitations, the most 

 serious of which arise from the fact that it is only in certain branches of chemistry 

 that it is possible to discuss general questions without referring to the properties, 

 and even to the idiosyncrasies, of individual elements and compounds. Thus, 

 while two hundred pages are devoted to the questions of equilibrium which are 

 usually dealt with as illustrations of the " phase rule," the whole of organic 



