March 7, 1878] 



NATURE 



359 



The author claims, as the chief results of his inductive 

 examination, to have determined from the monuments 

 the true values of the Sacred Hebrew or Royal Persian 

 cubit, the Royal Egyptian cubit, the Egyptian digit, the 

 Assyrian cubit, the ancient Greek foot, the Olympic foot, 

 the Drusian foot, the Plinian foot, and the Pythic foot, 

 together with the probable errors of these determinations. 



He claims also to have found that the principal standard 

 units of length were in more extended use than was 

 previously known, and to have indicated the countries in 

 which they were used. And also that he has brought 

 to light many other units of length of which the knowledge 

 had been previously lost. 



It is not probable, however, that all persons who have 

 given mature consideration to the contents of the work 

 will concur in the stated results or be altogether satisfied 

 with some of the mean units obtained. In every case a 

 unit deduced from the actual measurements is stated, and 

 not the measurements t'icmselves. But a large propor- 

 tion of these deduced units are not whole numbers of the 

 mean unit obtained from them. Thus, taking one of the 

 instances most favourable to the author's views, out of 

 twenty-eight Egyptian monuments, from which the mean 

 length of the royal Egyptian cubit is obtained, twelve 

 only of the deduced units are whole numbers, the others 

 being various fractions of the mean unit, and many of 

 tliem, such as 1, \, J, y\j, ^.y, |, f , ^^^, -^ are fractions not 

 marked upon any of the extant standard cubit rods, 

 which are divided only into seven palms and twenty-eight 

 digits. 



The essay will b^ read with much interest and advan- 

 tage by those persons who have given their attention to 

 metrological science. It appears to be a valuable 

 contribution to historical and ethnological literature, and 

 to be a ground-work for further researches on the subject. 



WOLF'S HISTORY OF ASTRONOMY 

 II. 

 Ccschichie dcr Asiroitomie. Von Rudolf Wolf. 

 (Miinchen : R. Oldenbourg, 1877.) 



IN our former notice of this valuable addition to astro- 

 nomical literature (Nature, vol. xvii. p. 259) 

 reference was made to the great amount of information 

 which the author has compressed within a moderate 

 space in the third and last section of his work which 

 treats of " the newer astronomy." We propose here to 

 take a brief survey of the principal contents of this por- 

 tion of the volume to assist the reader's appreciation of 

 the work. 



The third section is subdivided into four chapters — 

 9 — 12. The first commences, as before stated, with Sir 

 Isaac Newton's discovery of the principle of universal 

 gravitation, the publication of the " Principia," and the 

 first application of the new theory to the orbits of comets 

 by Halley, whose meritorious connection with the pub- 

 lication of Newton's immortal work is well known. This 

 is followed by some account of the foundation of the 

 Observatories of Greenwich and Paris, and soon after- 

 wards of those of Berlin and Copenhagen, whereby so 

 great an impetus was given to practical astronomy ; of 

 Richer's expedition to Cayenne for the determination of 



* Continued from p. 259. 



the solar parallax, fiom corresponding observations of the 

 planet Mars, and the first ideas as to the applicability of 

 transits of Venus for the solution of the same problem. 

 The labours of the earlier workers in the Newtonian 

 theory— of Bernoulli, Euler, Clairault, and others, are 

 particularised ; also Bradley's great discoveries of the 

 aberration of light and the nutation of the earth's axis, 

 together with his work in the field of observation, with 

 the similar work of Tobias Mayer and Lacaille. 

 Further on the same chapter treats of the labours 

 of Lagrange, Laplace, Gauss, and others in theory, 

 and of Herschel, Piazzi, Bessel, Struve, and others, in the 

 practice of astronomy. We have some account of the 

 " Theoria Motus," the " Fundamenta Astronomiae,'' 

 amongst classical works, and of progress made in the 

 solar, lunar, and planetary theories, and formation of 

 tables and ephemerides. Amongst the remaining varied 

 contents of this chapter there are notices of the discovery 

 of Neptune, stellar parallax, the connection between solar 

 spots and the earth's magnetism, the application of pho- 

 tography to astronomical purposes, and the introduction 

 of the spectroscope. 



Chapter lo is devoted to astronomical instruments and 

 their uses, after some remarks upon methods of calcula- 

 tion introduced in modern practice. There are brief 

 notices of instruments in their various forms, from the 

 complicated heliometer to the simpler appliances in the 

 hands of observers, with descriptions of many of the more 

 important purposes for which they have been brought into 

 use. The chapter concludes with a reference to La- 

 caille's memorable expedition to the Cape of Good Hope 

 and the expeditions undertaken on occasion of the transits 

 of Venus in 1761 and 1769. 



Chapter 1 1, on " The Structure of the Heavens," is 

 as varied in its contents, amongst which we may note : 

 The periodicity of sun-spots, and the new views upon the 

 physical constitution of the sun ; the ring of small 

 planets ; the zodiacal light ; the meteor-streams and their 

 connection with comets ; the physical condition of 

 comets ; the distribution of the stars ; the Milky Way ; 

 solar motion in space ; variable and double stars, and 

 binary systems ; stellar spectra, star clusters, and nebula?. 



In Chapter 12 we have an account of the principal 

 modern literature, periodical and otherwise, bearing upon 

 astronomical science in its various branches. There 

 are notices of the works of Weidler, Lalande, Bailly, 

 Montucla, Delambre, Littrow, Madler, and others, and of 

 such works as the Acta Ertiditoriwi, the Monatliche 

 Correspondenz and the Astronomische Nachj-ichtcn. 



It should be understood that the one chief advantage 

 which the student is likely to derive from Prof. Rudolf 

 Wolf's " History of Astronomy " will be a knowledge of 

 the authors, methods, &c., with which it may be neces- 

 sary for him to become acquainted in turning his atten- 

 tisn to any particular department of astronomy, an ad- 

 vantage that may not be immediately apparent from the 

 title of the work. Prof. Wolf does not enter into any 

 amount of detail, nor indeed would it have been prac- 

 ticable within the limits of this volume. But as affording 

 in comparatively brief space an accurate idea of the 

 gradual progress and actual state of astronomical science 

 and a valuable guide to any one entering upon its study, this 

 book may be confidently recommended. J. R. Hind 



