October ii, 1894J 



NA TURE 



567 



I preciable distance on each side of the continuous spectrum, 

 ' and with an open slit is a large circular disc about 6" in 

 diameter. The same appearance is noticeable in the 

 faint Hy and verj- faint Ha lines, but not in other lines. 



The section on Temporary Stars has also been very 

 considerably extended by the translator, by the addition 

 of a detailed account of the observations of Nova Aurig:v; 

 and of the various theories which have been proposed to 

 account for the manifold phenomena e.xhibited by this 

 object. The difficulties in the way of accepting any one 

 of these hypotheses as fully satisfactory are pointed out, 

 and it seems impossible to deny that there must have 

 been more than two bodies in action. The complete 

 transformation of the spectrum at the revival of the star, 

 so strikingly similar to that discovered by Copeland in 

 the case of Nova Cygni, is also an awkward fact to deal 

 with, and one that cannot be avoided by merely deny- 

 ing that we have here "a star turned into a planetary 

 nebula." The interpretation of the nebulous appearance 

 of the star as caused simply by the chromatic aberration 

 of the blue hydrogen rays, when the telescope is focussed 

 for the most intensive rays of the chief nebular line 5002, 

 I cms untenable, as so e.xperienced and sharp-sighted an 

 'iiiierveras Prof. Barnard has recently declared himself 

 to be absolutely sure, that the nebulous appearance is 

 not a mere telescopic effect [Aslr. Nach. 323S). And 

 why should we think it impossible for the object to look 

 like a nebula, when it has the unmistakable spectrum 

 of one, and when we remember the above-mentioned 

 observation by Campbell of D.M. 30", 3639.'' The 

 objects which caused the outburst in December 1891 

 j probably left the scene of the catastrophe a few months 

 I after, leaving behind them masses of gas both visually 

 I and spectroscopically seen as a nebula. But, as pointed 

 out by Prof. Frost, the most difficult facts to explain are 

 the enormous relative velocities of the objects. 



The study of the spectra of Type IIL; has, during the 

 1 ist few years, produced results which have very much 

 lessened the supposed similarity between these spectra 

 .Tnd those of sun-spots, and the development of bright 

 lines in many spectra of long-period variables at their 

 epochs of maximum obliges us to give up the ideas which 

 foniierly prevailed with regard to these variables. Here, 

 I as in the case of Nova Aurigie and /3 Lynt, we have evi- 

 1 dently to do with very complex phenomena. The trans- 

 luor refers in a few words to the theory advanced by Mr. 

 l.ockyer, that the long-period variables may be systems 

 I of two swarms of meteorites revolving in elliptical orbits, 

 and he dismisses it with the objection (which is not new) 

 ihnt the conditions in a system of this kind could not be 

 permanent, as with successive collisions the smaller swarm 

 would become spread out into a ring, thus causing the 

 variability to cease. This objection is, however, not a 

 serious one, as our own Leonids, though spread out into 

 a ring, have for many centuries exhibited a very strongly 

 marked maximum. 



After describing the spectra of Type III/;, the trans- 

 lator gives a summary of Pickering's statistical examina- 

 tion of the Draper Catalogue. He has omitted the short 

 notice of the Meteoritic Hypothesis which Dr. .Scheiner 

 had inserted at the end of this chapter, and which 

 hardly gave a fair ide.i of the hypothesis. The two 

 remaining chapters are devoted to the spectra of the 



NO. 1302, VOL. 50] 



Aurora and Zodiacal Light, and the displacements of 

 spectral lines as caused by the rotation of the sun, the 

 motion of stars in the line of sight, or by spectroscopic 

 binaries. A useful addition is given in the shape of a 

 reprint of Campbell's formulae and tables for the reduc- 

 tion of observations of displacement. 



The fourth part of the book (pp. 361-426) contains a 

 very valuable set of spectroscopic tables, viz. Rowland's 

 new table of standard wave-lengths {Astronomy arid 

 Astrophysics, April 1893), Abney's wave-lengths of lines 

 in the ultra-red spectrum, Kayser's and Runge's arc 

 spectrum of iron, a catalogue of stars of classes \\\a and 

 1 11^, and, lastly, an unpublished partial revision of the 

 chromospheric lines by Young. Finally, on pp. 427-472, 

 a bibliographical list is given of books and papers 

 relating to astronomical spectroscopy. This list is 

 unfortunately very incomplete, and glaringly so with 

 regard to solar phenomena. We have, also, in several 

 cases missed references to papers quoted in the body of 

 the book, and in others only found references to short 

 notices in Nature, instead of to original memoirs. 



On the whole, this English revised edition is a great 

 improvement on the original, valu.ible as the latter un- 

 doubtedly was, and it forms both an excellent text-book 

 for the student and a useful book of reference to workers 

 in spectroscopy. J. L. E. Dreyer. 



AGRICULTURAL ZOOLOGY. 

 Agricultural Zoology. By Dr. J. Ritzema Bos, Lecturer 



in the Royal .Agricultural College, Wageninen, Holland. 



Translated by J. R. Ainsworth Davis, B.A. With 



an introduction by Eleanor A. Ormerod. (London : 



Chapman and Hall, 1S94.) 



* GRICULTURISTS will be misled by the title of 

 r\. this book, if they expect to find any reference in 

 it to farm animals which especially interest and concern 

 them, such as horses, cattle, sheep, and pigs. There are 

 no descriptions of these animals in this work upon agri- 

 cultural zoology, although after having enumerated the 

 thirteen orders of mammals, Dr. Ritzema Bos says he 

 shall "deal only with those of agricultural importance," 

 and forthwith leaves out all references to cattle, horses, 

 sheep and pigs. But, on the other hand, such animals as 

 wild boars, deer, otters, golden eagles, nightingales, herring- 

 gulls, and grebes, having no connection with agriculture, 

 are treated of at some length, and figures of them are 

 given. Cuttle-fishes and star-fishes also seem out cf 

 place in a work entitled " Agricultural Zoology," which 

 should rather have been styled " Zoology, or the Ele- 

 ments of Zoology." 



Among the insects the migratory grasshopper (Acri- 

 dium inigratorius) and the Colorado beetle {Doryphora 

 dcccmlincata) figure, though these are not British in- 

 sects, nor are they likely ever to gain a foothold in this 

 country. .\ work upon British .Agricultural Zoology is 

 much wanted that would give the cultivators accurate 

 information upon all the animals that are in any way, 

 directly or indirectly, serviceable to them, and all those 

 that are harmful to them, directly or indirectly. Dr. 

 Ritzema Bos just touches the fringe of this subject with 

 regard to the larger animals, though, it must be admitted, 



