6o4 



NATURE 



[April 28, 1898 



•doors and windows are well arranged, but the joints at 

 the feet of principal rafter and tie-beam in Figs. 245, 

 246, 247 and 24 8, will not, it is hoped, be repeated in 

 succeeding volum es. The chapters on the resolution of 

 forces, mechanical contrivances, bending moments, &c., 

 give a prominent place to the scientific part of the sub- 

 ject, a study which we can with confidence advise the 

 •craftsman to undertake. The chapter on the deter- 

 mination of stresses might be made somewhat clearer, 

 liaving regard to the class of man for whom the book is 

 intended, if the author would take the forces acting at any 

 point always in the same order, and work round with the 

 sun. Under "mechanical contrivances" no mention 

 appears to be made of the screw, which is specially 

 imentioned in the syllabus. We refer with regret to the 

 fact that there is no index, which detracts materially 

 from the value of a well-arranged book. 



A GERMAN POPULAR ASTRONOMY. 

 Das Weltgebdiide. — Eine gemeinverstdndliche Himmels- 

 kunde. Von Dr. M. Wilhelm Meyer. Mit 287 

 Abbildungen im Text, 10 Karten, und 31 Tafein, im 

 Farbendruck, Heliogravure und Holzschnitt. (Leipzig 

 und Wien : Bibliographisches Institut, 1898.) 



IN a very handsome volume, well written, well printed, 

 and well illustrated, Dr. Meyer has given us the 

 main results of astronomical observation. We may 

 ■congratulate both the author and his readers on the 

 selection of the facts that has been made, and submitted 

 to consideration. The arrangement of the material has 

 •evidently been the subject of much care and thought ; 

 but we cannot say that the final result commends itself 

 •entirely to our judgment. In a short preface. Dr. Meyer 

 has intimated the general principles by which he has 

 been guided in preparing his work. He has wished the 

 reader to appreciate the grounds on which certain truths 

 "have been received, and not simply accept the assertions 

 as an outcome of authoritative teaching. He admits 

 that without mathematical symbols and analysis it may 

 be difficult to offer direct proof in support of many state- 

 ments ; but by translating the results of mathematical 

 deductions into the language of ordinary life, he thinks 

 it possible to find an efficient substitute. It is not without 

 a feeling of apprehension that one reads of threats of 

 this kind. Efforts to reproduce mathematical results 

 without the use of the necessary machinery generally 

 prove wearisome to the mathematician, and unintelligible 

 to the ordinary reader. But Dr. Meyer has not taken 

 the matter too seriously, and even in his chapter on the 

 Newtonian system avoids the perils of adhering too 

 closely to his own principles. 



The author has divided his book into two parts. The 

 first is descriptive, and in this section his endeavour is to 

 describe the whole universe as it may be seen with 

 instruments particularly designed for special ends. The 

 -causes for these appearances, or the theories by which 

 they may be explained, are reserved for the second part. 

 Whether such an arrangement is satisfactory can only be 

 decided by the student. To any one who approaches the 

 book with a fair amount of astronomical knowledge, it 

 appears cut in halves, without sufficient reason. As it is 

 impossible within a limited space to describe each section 

 NO. 1487, VOL. 57] 



separately, the author's method of treatment may be 

 illustrated by referring to the description of the moon, 

 given in the first section, immediately after describing, 

 not at too great length, but adequately, the telescope and 

 spectroscope and the processes of photography and 

 photometry. We have first of all an account of the 

 phases, for the detection of which no telescope is neces- 

 sary, and for whose correct explanation but little ingenuity 

 is required. The instrumental examination of the moon 

 begins with the application of the spectroscope to the 

 light, and the obvious deductions that follow its use are 

 necessarily given. Having discussed the absence of an 

 atmosphere, the effect of the sun's heat, &c., we get to 

 the telescope and trace historically the cartography of the 

 moon from Hevel to Schmidt. Finally, and also following 

 chronological order, we reach the age of photography and 

 the delineations of Weinek from the Lick negatives, many 

 of which are reproduced. Particularly good and inter- 

 esting are the comparisons instituted between portions of 

 the lunar surface and certain districts on the earth, not 

 by any means with the view of suggesting that the con- 

 figurations have been produced by similar processes in 

 each case, but as a convenient way of illustrating points 

 of resemblance or emphasising points of difference. The 

 Island of Corsica, the Colorado Cafion, the Yosemite 

 Valley are all in turn discussed and made to illustrate 

 some generic feature on the lunar surface. Altogether it 

 is the best description of the moon we have read ; and it 

 is only when we come to remember what is omitted, that 

 we have any sense of dissatisfaction. For instance, we 

 find nothing about the distance of the moon, though the 

 diameter is given. This is surely a departure from the 

 rule to be purely descriptive, though the description gains 

 immensely by it, since it enables comparisons to be 

 drawn between similar features on the earth. Moreover, 

 while the distance remains undetermined, the diameter 

 must be taken on authority ; and this is opposed to the 

 fundamental canon of the preface. The geometry of 

 eclipses has to be relegated to the second part, similarly 

 with other phenomena depending upon the mass of the 

 moon, such as the action of the tides or the effects of 

 precession and nutation. The advantage of the arrange- 

 ment does not seem evident, nor does it entirely fulfil the 

 purpose for which it was designed, although each part is 

 admirable in itself, but wanting in completeness and con- 

 nection. The method pursued with the moon is continued 

 throughout the solar system, though of course there is 

 not always the same necessity to return to omitted 

 portions. From the members of the solar system we 

 pass to comets and meteors, and finally to the universe 

 of the fixed stars. It goes without saying that these 

 chapters are not only correct, but offer us the latest in- 

 formation drawn, as they are, from experts in their several 

 branches of investigation. For the author, distrustful of 

 his own knowledge, and remembering that the fact of 

 to-day is liable to be displaced by the newer discovery of 

 to-morrow, prudently placed his manuscript for correction 

 in the hands of various authorities. Thus, Schiaparelli 

 either describes or confirms the description of Mars, and 

 Dr. Scheiner, of Potsdam, is responsible for the accuracy 

 of the chapters on spectrum analysis. Dr. Ginzel, who 

 has written so largely on ancient chronology, is willing 

 to assist here in the discussion of eclipses, while Dr. 



