2l6 



NA TURE 



\_yan. II, 187 



liquid. The temperature of the German bottom fermenta- 

 tion varies from ^"'^ C. to 7° C, a temperature that can 

 only be maintained by the employment of large quantities 

 of ice. 



The bottom and top yeasts are probably distinct species. 

 M. Pasteur, however, seems to be in error in stating 

 (p. 190) that the bottom yeast may be distinguished by 

 being less spherical than top yeast. It is true that in 

 London and Edinburgh yeast the cells will be found 

 usually round ; hard water, however, such as that at 

 Burton, or artificially made so, yields yeast in which the 

 cells are distinctly ovoid in appearance, resembling very 

 closely Bavarian bottom yeast. M. Pasteur further states 

 (pp. 188 and 192) that the bottom yeast yields a beer of 

 finer flavour, and hence argues the replacement of ales 

 produced by top fermentation by those made on the 

 Bavarian system. Here surely he must be thinking 

 rather of the inferior products of the surface fermentation 

 in France and Germany than of those of England and 

 Scotland. His assertions (pp. 12-17) that by bottom fer- 

 mentation store beers can be produced, whereas those 

 produced by top fermentation must be consumed at once 

 and cannot be transported are certainly strange to an 

 Englishman. 



So far from these unfavourable comparisons being true 

 in all cases, the exact opposite is generally the case. 

 Bavarian and other bottom fermentation beers are in fact 

 those which can neither be preserved nor transported 

 without the liberal employment of ice ; even that sent 

 from Vienna to London must be kept cold artificially 

 in order to avoid rapid destruction. As regards flavour, 

 there are many who think a glass of Burton pale ale or of 

 good old college rent ale to be superior to any Bavarian 

 beer. The chief cause of the decline in the production 

 of top fermentation beers on the Continent has been the 

 want of attention in the fermentation process, whereas 

 the English brewer, especially the brewer of high-class 

 ales, has been unremitting in his attention to the tempe. 

 rature in fermentation and to the perfect cleansing of the 

 ale. Now where such attention is given it is not difficult 

 to obtain ales which will keep a few years. While object- 

 ing to our English produce being so hastily depreciated 

 by M. Pasteur, our brewers will be the first to avail them- 

 selves of his biological researches in order to render their 

 produce more stable and better flavoured, without having 

 recourse to the general adoption of the vastly more costly 

 system of bottom fermentation. 



Let us now leave this question of the respective value 

 and future development of the two systems of fermenta- 

 tion, and assume that by either the one process or the 

 other we have obtained our glass of beer. The question 

 now naturally presents itself to us, as to others before us, 

 to what is fermentation due ? Pasteur's answer to this I 

 propose to discuss next week. 



Charlks Graham 



OUR BOOK SHELF 



Manual of the Vertebrates of the Northern United States. 

 By David S. Jordan, M.D. (Chicago : Jansen, McClurg, 

 and Co., 1876.) 



This useful work contains a short diagnostic account of 

 the whole of the vertebrated animals of the Northern 

 United States, and has been written, as the author tells 



us, to give collectors and students who are not specialist 

 a ready means of identifying the families, genera, an 

 species described. The mammals as well as the birds ( 

 North America have been so ably and elaborately treate 

 of by Prof. Baird, Dr. Coues, and others, (hat those wh 

 are studying these branches of zoology will not find th 

 smaller volume of special service, nevertheless we are n( 

 acquainted with any work having a range of treatmer 

 which includes the reptilia, amphibia, and fishes with th 

 two other classes. The sub-kingdom, as well as eac 

 class and order, are concisely defined, and the mo! 

 modern arrangement is adopted, based upon the be; 

 authorities, the relative importance of the characterisin 

 features being clearly brought forward. The system ( 

 employing artificial keys so useful in botanical determine 

 tions, and so successfully employed by Dr. Coues in orn 

 thology, is employed throughout the book, and will, n 

 doubt, be found to work well. A glossary of the princip; 

 technical terms used in the body of the book is als 

 appended. As an example of the manner in which th 

 different species are described, we will take that of one c 

 the species of Fly-catchers : " Empidonax acadicus (Gm. 

 Baird. Small Green-crested Fly-catcher. — Clez 

 olive-green ; wing bands buffy ; whitish becoming ye 

 lowish below ; yellowish ring about eyes ; bill pale below 

 primaries nearly an inch longer than secondaries ; secont 

 third, and fourth primaries nearly equal, and much longt 

 than first and fifth ; first much longer than sixth ; L. 6 

 W. 3 ; T. 2|;Ts. f; Tel. ^ ; E.U.S. frequent." T 

 naturalists on this side the Atlantic the work will b 

 found a valuable one of reference on account of its inch 

 siveness, and a glance through it makes us feel how usefi 

 a similar one on the British vertebrate fauna would prov 

 to students and collectors. 



The Emigrant and Sportsman in Canada. By John ^ 

 Rowan. (London : Stanford, 1876.) 



This is a capital book in many respects. Mr. Rov/a 

 is himself an old Canadian settler and knows th 

 country well in various aspects. He tells the plai 

 truth as to the suitability of Canada as a field fc 

 emigration, and the intending emigrant could not get 

 better guide as to the resources of the country, and th 

 kind of settlers for which it is adapted. Mr. Rowan is 

 keen sportsman and has a fair knowledge of zoology 

 His descriptions of hunting life in Canada are thoroughl; 

 interesting and abound with fresh information on th 

 many animals which are still to be found there. Mi 

 Rowan is a good observer, and some of the informatio: 

 which he gives regarding the animals with whose habit: 

 he is familiar may be new even to naturalists. Hi 

 describes, at considerable length, especially, the habits 

 the beaver as observed by himself, and adduces som 

 facts to show that previous popular statements witl 

 regard to this animal must be to some extent modified 

 The volume will be found of interest not only to th 

 emigrant, the sportsman, and the naturalist, but to a) 

 who love good hunting and trapping stories well told. It 

 principal defect is the want of an index. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions exprei^ 

 by his correspondents. Neither can he tender take to rett^ 

 or to correspond with the writers of, rejected manuscr 

 No notice is taken of anonymous communications.'] 



On a Mode of Investigating Storms and Cycloned 

 I SCARCELY know anything more interesting in connectio 

 with the investigation of cyclones and of our storms than th | 

 theoretical investigations of Reye, Mohn and Guldberg, and th , 

 practical ones of Mr. Clement Ley. Mr. Ley's papers in thi 

 fournal oi the Scottish Meteorological Society, iv. 66, 149, 33(j 

 have especially attracted my attention. We have to study th! 



