NA TURE 



49 



TEXT-BOOK OF COSMICAL PHYSICS. 



Joh. Mullet^ s Lehrbuch tier Kosmischen Pliysik. Fiinfte 

 umgearbeitete und vermehrte Auflage, von Dr. C. F. 

 [ W. Peters. (Braunschweig : Friedrich N'ieweg und 

 Sohn, 1S94) 



NEARLY everyone who has become at all acquainted 

 with popular German scientific works will have at 

 sometime fallen in with this well-known book by Dr. 

 Miiller. It first appeared in the year 1856, and received 

 particular favour, in that in the first place it was really 

 popularly written, and secondly, that it was useful as a 

 book of reference for many questions which dealt with 

 every-day phenomena. The book reached its fourth 

 ] edition in 1875, and since then none other has appeared, 

 except the one that we now have under consideration. 

 Nineteen years have thus flown by since Dr. Miiller 

 undertook the last revision, and in this period one is not 

 at all surprised to find that accepted views on many points 

 have undergone great changes, and in some cases entire 

 Irevolutions. 



I For those of our readers who have not had the oppor- 

 itunity of examining previous editions for themselves, a few 

 Iwords as to the gap which the author intended that the 

 work should fill may not be out of place. Referring, in the 

 preface to the first edition, to the great stir Humboldt's 

 " Kosmos " made throughout Germany, attracting general 

 attention to the study of cosmical phenomena, he stated 

 that he intended to produce a work, in the form of a text- 

 book, in which the physics of the heavens and the earth 

 should be systematically brought together. In astronomy 

 it was true that many p ipular works were at hand, but in 

 physical geography and meteorology they were to a 

 rertain extent wanting. With such an object in view it 

 was necessary to keep the book within certain limits, and 

 ;not to enter too far into mathematical developments : 

 ihis accounts for the brevity of some parts in the astro- 

 nomical and optical sections. On the whole, however, a 

 ion-mathematical reader should rest very content with 

 what he has before him. 



In this new edition. Dr. Peters, who has undertaken the 

 ■evision,has not deviated from the original idea of dividing 

 ihe work into four books, and they are, as formerly, devoted 

 ,0(1) the movements of the heavenly bodies and their 

 tnechanical explanations ; (2) cosmical and atmospheric 

 ohenomena ; (3) heat phenomena on the earth's sur- 

 |ace and in the atmosphere ; and, lastly, (4) atmospheric 

 ilectricity and terrestrial-magnetism. 



Covering as the work does over 900 pages, a systematic 

 reatment of each section would be impossible, so we will 

 mit ourselves to searching out what is not in the book 

 'hich ought to be there, and vice versa. With regard to 

 he latter, with the exception of what is referred to later 

 )n, there is not much that need be said, except it be that 

 ome old incidents of observed phenomena might have 

 nade place for others more recent, as, to take one ex- 

 •mple, that referred to under " Magnetische Storungen " 

 P- 858). 

 The first book, dealing with astronomical phenomena 

 NO. 1281, VOL. 50] 



consists of over 300 pages, and is the largest of the 

 four. This has received many and various alterations 

 and additions ; among the latter may be mentioned 

 references to the new moons of Mars and Jupiter, the dis- 

 coveries relating to the periods of rotation of Mercury 

 and Venus (Trouvelot's work somehow being overlooked 

 here), variable stars of the Algol type, and photographic 

 and spectrum analysis work. Those important 

 phenomena, the tides, receive due attention, and 

 instead of being dismissed in two pages, as in the last 

 edition, in this one have twelve devoted to them. In the 

 section on time, it is a pity that more is not said about 

 the new system of time-zones, for this is just a typical 

 point to which an ordinary reader might wish to refer. 

 Under the description of what we know about the planet 

 \'enus, there are several important points which do not 

 receive mention. Thus, for instance, no reference is 

 made to the snow-caps of which Trouvelot has published 

 so many drawings, nor can an account be found of the 

 curious and quick changes which have been observed to 

 occur on the terminator and limb, and which afford 

 strong arguments in favour of a rapid rotation of the 

 planet. The transit of Venus, on the other hand, is fully 

 discussed and described. 



In the chapter dealing with comets, excellent de- 

 scriptions are given of their gravitational motions, and of 

 remarkable appearances, while the forms of their tails 

 are discussed at some length. During the last few years 

 astronomers have had many opportunities of studying these 

 bodies, and our knowledge has very much increased. Thus 

 v.e now generally suppose them to be swarms of meteorites 

 under the influence of gravitation pursuing their course 

 round the sun, the particles of which they are composed 

 banging and clashing about near perihelion, and produc- 

 ing light and heat. One might at first be led to consider 

 that the author had overlooked such new knowledge, as 

 the reader is pulled suddenly up by a section on the 

 "meteorite." It is not till after twenty-five pages have 

 been passed over that he is informed of this suggested 

 relation between comets and meteors, and then in only 

 a few words. This subject is mentioned again briefly 

 under the spectra of comets. 



Coming now to the second book, our luminary the sun is 

 the first dealt with. In this part we may mention one or 

 two points which we think are deserving of more attention . 

 Thus, a propos of sun-spots, such an absorbing question 

 as the unequal period between a maximum and a minimum 

 and a minimum and a maximum receives no mention, 

 or even the important fact of the latitudinal changes 

 that the positions of spots undergo during a period; in 

 fact, in fifteen lines the whole reference to spot-period is 

 treated. In the explanations given to account for spots, 

 ZoUner's ideas are the most modern hinted at ; there is 

 no statement as to our present view, that they are caused 

 by down-rushes of cooler matter from the upper regions 

 of the solar atmosphere. 



.'\n interesting account of the zodiacal light is followed 

 by a section on planetary photometry, in which G. 

 M tiller's recent work is referred to. In the section on 

 variable stars, the Algol type is fully dealt with, but no 

 attempt is made to explain other kinds of variables, 

 although several plausible suggestions are at hand. 

 Under temporary stars exactly the same is the case, in 



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