Junk 13, 1895J 



NATURE 



149 



The Migrations of the Lemmings. 



Ai.TIKU'iiH I have dwelt aiiion^; the Lemmings for many 

 years, and paid great attention to their migrations, I have 

 thought it might be more satisfactor)- to my readers to record 

 the result of an interview with a captive member of the tribe, 

 as recorded by the aid of a phonogra|ih, assisted by a certain 

 legitimate amount of amplification which the poverty of the 

 language necessitates. This, hoHever, I am convinced is what 

 my little prisoner intended to say. " I am amused by the 

 reasons men give for our sudden appearances and inexplicable 

 migrations. But, although I do not see why I should enlighten 

 \ou on either of these pf>ints, esj^ecially as you wouki probably 

 only stick the harder to your own opinion, I will venture to ask 

 whether you think we cross wide lakes, the oi)jDosite shores of 

 which are quite invisible to us, in order to find the food 

 which we thus aliandon ; indeed, though I fear I am somewhat 

 letting what you call the cat out of the bag by saying it, I have 

 often wondered why I myself did not wander along the green 

 shores of Heimdalsvand and down the valley amid sweet grasses 

 and clover, instead of swinmiing across lo barren Valders, and 

 getting caught by you for my pains. But, after all, it is no worse 

 than when my friends the swallows leave their flies, and even 

 their families, and start on their travels, when the impulse seizes 

 them, whilst the former are still plentiful, and the latter not yet 

 ungrateful. .So I feel indignant at the suggestion that we travel 

 Iwcause we are overcrowded and underfed at home. I admit 

 that our temper as a race ij somewhat short; it has been iir- 

 l>aired by incessant bullying. Dogs, wolves, and lynxes eat us 

 wholesale ; and the reindeer tlisgustingly declare that we are a 

 mere bag of succulent saitr-hrattt. .Shadows annoy us. and you 

 men have even invoked spiritual weapons to aid your carnal 

 implements of destruction. Btit let me seriously advise you not 

 to fling about inappropriate epithets ; our customs are at least as 

 good as your own, anil i)robably somew hat older, for we too have 

 had an ancestry, and nobhsse oblige. Enough ; let me out ; I 

 want to get on." W. Dlita-Crotch. 



Richmond. Surrev. 



over nearly seven of ilic ten volumes projected. It 

 is almost a Cambridge work in a double sense, for 

 'rof. Hcrdman, who is to write 



THE CAMRRIDGK NATURAL IflSTORVy 

 A LTHOUCH the third in the series, this volume is 

 ■' *■ the first of the long-promised " Cambridge Natural 

 History "to appear, and as such excites additional interest 

 because it affords some clue to the probable style of the 

 remainder- probable, since "complete uniformity of 

 treatment has not," wc are told, "been aimed at. It is 

 worthy of remark that, contrary to what obtains in 

 most popular works on natural history, the In\crtcbrates 

 are to receive their fair share of atteiition, and to extend 



I "The C.imhridKc Natural History." Kdiled by S. K. Harmcr. M..\. 

 ?- /■ w .^'•'I'l'^y. M.A. Vol. iii. "MoHuscs." By the Rev. A. H. 

 Looke .M.A. •• Hrachiopods •■ (Recent). By A. K. Shipley, M.A. 



Brachiopods (Fossd). By F. R. C. Reed, M.A. Pp. vii. 51s: ,« 

 higurcs ii> lexl, and j Maps. 8vo. (London : M.icmillan and Co., 1895.) 



with the exception of 



on the " .Ascidians and Amp/iicxiis" and Mr. F. E. 

 Beddard, who will undertake two such widely separated 

 subjects as " Earthworms and Leeches" and " Mammals," 

 all the contributors are connected with that University. 



" 'I'he Cambridge Natural History' is intended, "the 

 publishers announce, "in the first instance for those who 

 have not had any special scientific training, and who are 

 not necessarily acquainted with scientific language. .\l 

 the same time an attempt is made not only to combine 

 popular treatment with the latest results of modern 

 scientific research, but to make the volumes useful to 

 those who may be regarded as serious students in the 

 various subjects. Certain parts have the character of a 

 work of reference." 



By this standard, then, the present volume must be 

 judged; and on opening its leaves and turning over its 

 pages, with their abundance of new and beautiful illus- 



Boltzmann's Minimum Theorem. 



There is a |X)int of great interest, in connection with Mr. 

 Btirbury's letter in your issue of May 30, on which he has not 

 touched. 



The expression obtained in the Boltzmann theorem for the 



value of , depends on the assumption that the actual dis- 

 tribution is at every instant absolutely identical with the most 

 probable distribution. This we know cannot be exactly true. 



Therefore the 'alue of , in Boltzmann's theorem is not iden- 

 tified with the /«<7j//*TO*a/5/e- value of . It is, for instance, 



de 

 <(uile possible, in the absence of proof to the contrary, that no 

 matter in what way the actual ilistribution difiers from the most 



1 ti ■ ""l' 



])rotjat)le one, the actual -. may be numerically smaller than 



the value corresponding to the most probable distribution. 



In that case Boltzmann's theorem would give the maximum 

 rate of subsidence instead of the most probable rate. Can -Mr. 

 Kurbury or Dr. Boltzmann throw any light on this question ? 



EdwI). r. ClI.VERWEI.I.. 



Trinity College, Dublin, June i. 



NO. 133;, VOL. 52] 



Kic. 1. — Chiton Spinosiis, Brus. 



trations, it is at once manifest that artist and engiaver, 

 printer and publisher, have vied with each other to pro- 

 duce a work worthy of the conception. 



The major portion, or, to be precise, 459 pages of the 

 whole, is devoted to the .Mollusca. It is no fault of the 

 authors if it has to be admitted that a treatise on this 

 branch of natural histoiy, at once popular and scientific, 

 still remains to be written. Mr. Cooke, who is respon- 

 sible for this section, save for a casual passage or phrase 

 here and there, has produced a most readable work : but 

 the burden laid on his shoulders is greater than one man 

 can bear nowadays, for no single individual can be a 

 specialist in all the numerous branches of the subject; 

 and yet nothing short of special knowledge in every 

 ramification is adequate for the production of a text- 

 book. The co-operation of specialists is yearly becoming 

 more and more of a necessity in compiling manuals if 

 good work is to be achieved, and in our opinion the 

 system of minute subdivision, adopted for example in 

 the " Standard Natural History," which was published 

 some years ago in .America, is the only wise one. 



It is not, therefore, any matter for wonder that Mr. 

 Cooke has h;id to resort largely to compilation, with the 

 inevitable result that facts here presented in one form of 

 phraseology, would, with a more intimate personal know- 

 ledge, have been difierently expressed. Thus, for example, 

 when speaking of barriers to distribution, we are told that 

 "ranges of inferior .iltitude, such as the Pyrenees, the 

 Carpathians, and the. Alleghanies, may be turned in flank as 

 well as scaled," and when he wiote, "The Mediterranean 

 offers no effectual barrier" the author evidently did not 

 take into consideration the altered distribution of sea and 

 land in the Mediterranean region during I'lcistocene 



