NATURE 



i8i 



THURSDAY, APRIL 15, 1909. 



POPULAR SCIENCE. 

 (i) Astronomy of To-Day. A Popular Introduction in 



Non-Technical Language. By the late Dr. Cecil 



G. Dolmage. Pp. 362 ; illustrated. (London : 



Seeley and Co., Ltd., 1909.) Price 55. net. 

 (2) Scientific Ideas of To-Day. Popularly Explained. 



By Charles R. Gibson. Pp. 344; illustrated. 



(London : Seeley and Co., Ltd., 1909.) Price 55. 



net. 

 (l) A 1 WHILST possessing- a thorough knowledge of 

 »V any science, it is often found to be a diffi- 

 cult matter to coordinate one's facts so that the novice 

 shall be at once sufficiently interested and efficiently 

 instructed ; but the former of these two works 

 demonstrates to us that the ideal is not unattainable; 

 the late Dr. Dolmage succeeded in a task in which 

 .so many writers have failed. 



By the arrangement of the various branches of the 

 subject, the reader is ever led from coordinated 

 generalities to the more specific details, and is always 

 prepared for what he is reading by the knowledge 

 acquired from the previous chapters. Thus, while 

 the general features of the solar system are 

 expounded in the third chapter, the various members 

 of it are not discussed in fuller detail until chapters 

 xii.-xviii., the reader meanwhile being prepared for 

 this fuller treatment by carefully reasoned chapters 

 on gravitation, celestial distances and magnitudes and 

 their measurement, eclipses, the evolution of methods 

 of observation, and spectrum analysis. 



Occasionally it appears that the endeavour to 

 employ only popular language has resulted in some 

 ambiguity. Thus the term " thicker " is applied to 

 the sun's successive layers when, as shown in the 

 succeeding paragraph, "denser" was presumably 

 intended; but such slips are few in number and, to 

 the general reader, comparatively unimportant. 



In describing the planets the author accepted the 

 conventional terminology, but protested against the 

 use of " inferior " and " superior " instead of the 

 more generally descriptive terms "interior" and 

 "exterior"; certainly for the general reader the 

 latter terminology appears to be preferable. 



The discussion of Martian features, and their 

 imports, is a difficult one for any writer of the present 

 day to tackle, but in this volume the reader is given 

 a very clear and concise statement of the various 

 theories and their corroborative observations. 



Tlie chapters which follow deal in the same 

 popular — yet scientific — manner with comets, meteors, 

 the stars and the universe, and an interesting volume 

 is brought to a close by two chapters dealing 

 respectively with the beginning and the ending of 

 things, the latter containing a graphic, if terrifying, 

 picture of the collision of a dark sun with the solar 

 system. 



The twenty-four illustrations and twentv diagrams 

 have been carefully chosen and well reproduced, and, 

 with the clear statements of the text, they should 

 certainly open the eyes of the " general reader " to 

 most of the wonders of the universe surrounding him. 

 NO. 2059, VOL. 80] 



(2) Mr. Gibson's work, a companion volume of 

 the " To-Day " series, is also intended for readers 

 whose acquaintance with the latest concepts relating 

 to the matter and motion around them is of the 

 "general" order, and a great deal that has been 

 said above, concerning the good arrangement and 

 clear statements of Dr. Dolmage 's work may also 

 be said of this volume. 



The author's ideal is to explain in popular language 

 how the matter around us is built up and how the 

 energy affecting that matter is transformed, trans- 

 mitted, and received. No previous knowledge of 

 science or mathematics is assumed; all that the 

 reader has to do is to take the subjects in the order 

 in which they are discussed ; he will then find that no 

 serious difficulties occur because his previous reading 

 has prepared him for what follows. 



.\ marked feature of this book is the number of 

 analogies by which the various actions and inter- 

 actions are illustrated. These are selected frorn 

 everyday life, and are always apt and illuminating, so 

 that totally new ideas concerning, say, the construc- 

 tion of the atom, the nature of electricity, the causes 

 of radio-activity, and like subjects are always clothed 

 in a familiar garb. 



The subjects dealt with are too diverse to treat 

 seriatim in a brief notice, but they may be classified 

 under the headings matter and its construction, the 

 nature, measurement, and perception of various forms 

 of radiation, energy and its transmission, gravity, 

 the aether, and the origin of life. We are thus 

 introduced to the latest ideas concerning electrons, 

 the dissociation and association of atoms, radio- 

 activity, spectrum analysis, action at a distance, and 

 the origin of life and matter. In every branch the 

 author remembers that he is endeavouring to reach 

 minds previously ignorant of such matters, and is, 

 therefore, very careful in his selection and definition 

 of terms. Thus, for example, in order to avoid any 

 possible ambiguity, he prefers " electrons " to 

 "corpuscles," and employs "aether " instead of the 

 " ether " now so often used, and in these and similar 

 cases he discusses the reasons for doing so. 



Four appendices give further information on 

 various subjects, and should prove very useful in 

 supplementing the necessarily brief explanations in 

 the book itself. The first of these gives the ingre- 

 dients of the world, i.e. the elements, their atomic 

 weights, and the order, with dates, of their dis- 

 covery. That these lists have been carefully 

 prepared is illustrated by the fact that, in the last, 

 helium is mentioned twice ; discovered in the sun, 

 by Lockyer, in 1868, and on the earth, by Ramsay, 

 in 1895. Appendix ii. outlines the history of the 

 modern theory of light, iii. gives particulars of 

 aether waves, and iv. describes, more fully, the 

 methods by which invisible electrons are counted and 

 measured. 



The forty illustrations are admirable ; instead of 

 the old-fashioned diagrams, with which he has been 

 regaled so often, the general reader will find here 

 reproductions of actual photographs, either of work- 

 ing apparatus showing just how the experiments are 

 performed, or illustrating clearly the results obtained. 



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