March 27, 18 90 J 



NA TURE 



4^5 



reproduction. The effects of this fertility of long-lived 

 people must give their stock an advantage in the race 

 for existence, so that one would expect their number, in 

 proportion to the rest of the population, gradually to 

 increase. 



The last chapter gives a short account of the maladies 

 of old people, and is chiefly of medical interest. 



Besides the general account of the subject, Prof. 

 Humphry gives all the analyses of the British Medical 

 Association returns, which furnish the material for the 

 book. There are several good photographic illustrations : 

 the frontispiece, portraits of a man and his wife (both 

 over loi years), and others, representing sections through 

 the neck of the thigh-bone, and the jaw of old people. 

 With regard to the femur, Prof. Humphry points out 

 that there is no foundation for the generally accepted 

 idea that the head in old people sinks to or below the level 

 of the great trochanter, and the illustration certainly bears 

 out his criticism. 



Perhaps the happiest feature of the book is its 

 optimism. " It is satisfactory to note how many of the 

 very aged are in good possession of their mental faculties 

 — taking a keen interest in passing events, forming a 

 clear judgment upon passing events, and full of thoughts 

 for the present and future welfare of others." 



An old age like this is worth striving to attain, although 

 one may never be free from the dread of dying " from 

 the head downwards," and so lingering on in 



" Second childishness and mere oblivion, 



Sans teeth, sans eyes, sans taste, sans everything." 



E. H. S. 



THE ELEMENTS OF ASTRONOMY. 



The Elements of Astronomy. By Prof. C. A. Young, 

 Ph.D., LL.D. (Boston and London: Ginn and Co. 

 1890.) 



'"T^HIS is a valuable addition to the existing text-books 

 ^ of astronomy for the use of those who intend to 

 study the subject seriously. It has much in common 

 with the same author's larger work on " General 

 Astronomy " (see Nature, vol. xxxix. p. 386), but we are 

 assured that it is not merely an abridgment, but has 

 been worked over with special reference to a high-school 

 course. It is assumed that the students have mastered 

 the ordinary elementary subjects, and are acquainted with 

 elementary algebra and geometry. 



The book covers quite as much ground as can be 

 expected for an elementary course, although many of the 

 subjects are merely glanced at. Practically everything, 

 with the exception of the more difficult problems of 

 mathematical astronomy, is considered more or less. 

 The opening chapters deal with definitions, the geometry 

 of the sphere, and the determination of latitude and longi- 

 tude. Chapters on the earth's dimensions and motions, 

 the moon, sun, planets, comets, stars, and nebulas, then 

 follow. An appendix includes topics which might be 

 considered beyond an elementary book, but are still of 

 sufficient importance to form part of a high-school 

 course. 



Astronomical physics receives a fair share of attention, 

 but here the book is necessarily more open to criticism 



than in the parts dealing with well-established facts and 

 principles. There are few general text-books which treat 

 this important branch of astronomy in a satisfactory 

 manner, and it is perhaps not to be wondered at, as the 

 constantly increasing number of new observations neces- 

 sitate considerable changes in our ideas. As far as a 

 consideration of the facts is concerned, however, Prof. 

 Young has done his work admirably, but this cannot be 

 said of his treatment of the various conclusions which 

 have been drawn from them. In his introduction. Prof. 

 Young tells us that he has tried to treat every subject in 

 such a way as " to discourage narrow and one-sided ways 

 of looking at things, and to awaken a desire for further 

 acquisition." However he may succeed with his readers, 

 it does not seem that he has altogether taken this lesson 

 to heart himself, for we find him dismissing suggestions 

 without a complete hearing. For instance, in connection 

 with the theory that sun-spots are formed by the down- 

 rush of cool materials into the photosphere (p. 130), he 

 states that it is not easy to reconcile this view with the 

 distribution of the spots over the sun's surface. Further 

 enquiry on his part, however, would have shown him 

 that the theory in its extended form suggests that the 

 spot-forming material is mainly formed of vapours which 

 have condensed in the cool outer layers of the sun's 

 atmosphere (in the same way as water-vapour condenses 

 in our own), and also gives an explanation of the way in 

 which the material may be localized over the spot-zones. 

 The author is notably cautious with regard to new things, 

 but we are surprised to find that he continues to adopt 

 Secchi's classification of star spectra (p. 317), seeing that 

 it does not satisfactorily treat bright-line stars like y 

 Cassiopeiae, and those of Orion which give almost con- 

 tinuous spectra. The classifications suggested by Vogel 

 and Lockyer both have the advantage of detail, and the 

 latter is certainly the most philosophical. On p. 318 it is 

 stated that stars of Secchi's fourth type usually " show a 

 few bright lines," in addition to the carbon absorption 

 bands, an idea of Secchi's which was shown to be 

 erroneous several years ago. 



The book is abundantly illustrated, and most of the 

 diagrams are excellent. Fig. 119, however, gives a very 

 bad impression of the spectrum of a nebula, the three 

 bright green lines being represented as almost equidistant, 

 whereas they practically form a triplet. A useful 

 " Uranography " is given at the end. This embraces the 

 more important celestial objects in the northern hemi- 

 sphere and some degrees south, and is accompanied by a 

 series of star maps. In the maps a convenient system of 

 indicating magnitudes is adopted, but it has the dis- 

 advantage of destroying the appearances of the constella- 

 tions for rapid identification. A. F. 



OUR BOOK SHELF. 



Physiology of Bodily Exercise. By Fernand Lagrange, 

 M.D. (London : Kegan Paul, Trench, and Co., 1889.) 

 This book at first sight reminds one of the saying that a 

 German takes a year to make a research, and a week to 

 write an account of it, while a Frenchman takes a year 

 to write a book on one week's work. The only original 

 part consists of a few experiments on the influence of 

 fatigue in producing increased excretion of urates in the 

 urine. The author ascribes most of the ill effects of 



