lOO 



NATURE 



[December 3, 1891 



Mr. Rockhill is of opinion that polyandrous marriages, 

 although frequently met with, are not by any means so 

 numerous in Tibet as we have hitherto been led to 

 suppose. Polyandry exists only in agricultural districts, 

 and he suggests that it is maintained there because the 

 tillable lands are of small extent, and every family feels 

 it to be important that the ancestral estate should not be 

 divided. This, however, as he himself points out, can 

 at best explain, not the origin of polyandry, but merely 

 the fact that the custom is still permitted to survive. 



We may note that the illustrations are excellent, and 

 that two good maps make it easy for the reader to trace 

 the author's route. 



SCIENCE AND BREWING. 

 A Text-book of the Science of Brewing. By E. R. 

 Moritz, Ph.D., and G. H. Morris, Ph.D. Based upon a 

 Course of Six Lectures delivered by E. R. Moritz at the 

 Finsbury Technical College. (London : E. and F. N. 

 Spon, 1891.) 

 "0 REWING is an industry which, as a rule, does not 

 -L' excite the interest in scientific minds that it de- 

 serves. The reason is difficult to explain, for there is 

 no industry which involves more problems of general 

 scientific moment, or makes more varied calls on the 

 different sciences. As an illustration— noting very briefly 

 a few points in the manufacture of beer— we have in 

 malting a study of the embryological development of the 

 barley plant, and the secretion and use by the growing 

 embryo of those curious enzymes which render both the 

 carbohydrate and proteid food of the endosperm avail- 

 able ; in the mashing, or infusion of malt with water, we 

 meet with the action of the enzyme, diastase, upon starchy 

 involving some of the most complex molecular changes 

 known ; and in fermentation, produced both by the 

 Saccharoniyces and Bacteria, we have all the interest- 

 ing difficulties connected with the morphology and 

 zymotic powers of these organisms. It is evident that any 

 technical scientific work on such subjects as those just men- 

 tioned, involves questions of the greatest general scientific 

 interest, and touches on points at the extreme limit of 

 our present knowledge ; consequently, it is not surprising 

 to find that science owes some most important advances 

 to scientific workers in the field of brewing. For 

 instance, our knowledge of the constitution of starch, 

 and the changes it undergoes during hydrolysis by the 

 action of acids and diastase, is almost entirely due to the 

 researches of C. O'Sullivan and of Horace Brown, both 

 connected with the industry of brewing. 



Dealing, then, as the science of brewing does, with 

 some of the most complex problems known, investiga- 

 tions in this field of work carry with them more than 

 ordinary technical interest, and should excite more 

 general interest in the scientific aspect of the industry 

 than seems to be accorded to it at present. A perusal of 

 Drs. Moritz and Morris's " Text-book of the Science of 

 Brewing" has induced us to make these remarks, for 

 contained in this work we find for the first time a lucid 

 and correct account of the important scientific prin- 

 ciples involved in the brewing industry, and the work 

 that has been done upon them. Although, of course, 

 mainly written for technical purposes, the authors have 

 NO. I 153, VOL. 45] 



treated the whole of their subject in such a manner that 

 the book undoubtedly has a general scientific value beyond 

 the circle of those for whom it is mainly intended. We 

 are sure that anyone wishing to look up such subjects as 

 starch and its transformations, or fermentation, would do 

 well to consult this work, for, apart from the admirable 

 rhtimes of our present knowledge on such subjects, the 

 abundant references given, to the authors quoted, are 

 themselves of much value. 



Hitherto there has been great want of a technical 

 guide to the scientific principles of brewing, nothing in 

 the least worthy of such a name having been published ; 

 and the unfortunate student of this subject has been 

 compelled to attempt the almost impossible task of col- 

 lecting his information from a literature scattered far 

 and wide, with no guide to teach him how to do it, 

 or how to select the good from the bad when it was 

 done. His difficulty is now over, we are pleased to say, 

 for in Drs. Moritz and Morris's work we find a technical 

 guide that ranks with the best of those written on any 

 subject, and we feel sure that it will assist in a marked 

 way in spreading a more general knowledge of the real 

 principles of the brewing industry. One aim of the 

 authors has been, not only to lay before their readers the 

 present state of scientific knowledge with regard to brew- 

 ing, but also by their experience as brewers to draw 

 practical deductions from this knowledge. This part of 

 their subject they have approached in a very fair and 

 impartial spirit, and they have not hesitated to call 

 attention- to those points on which knowledge is at 

 present too restricted to justify drawing deductions of 

 any value. Those who are acquainted with the quasi- 

 scientific writing that prevails in some of the brewing 

 trade periodicals, will thoroughly appreciate this. We 

 trust that the appearance of Drs. Moritz and Morris's 

 work will raise the general tone of technical brewing 

 literature, an end much to be desired. 



In attempting to write a text-book bringing the scien- 

 tific principles and the practice of brewing together, the 

 authors undertook a difficult task, and one that could 

 only be done by those who have a thorough grasp of 

 both branches of the subject. They have been most 

 successful in their effort, and we commend their work 

 to the notice of all students of brewing, and to all those 

 brewers who take a rational interest in their own busi- 

 ness ; such cannot fail to derive much benefit from a 

 careful study of it. 



A THEORY OF GRAVITATION. 

 Fresh Light on the Dynamic Action and Ponderosity oj 

 Matter. By " Waterdale." (London : Chapman and 

 Hall, 1891). 



THE original aim of this work was the discovery of 

 some reason, other than the hypothesis of attrac- 

 tion, to account for the gravitation of one body towards 

 another. 



The writer thus takes up the subject of gravitation 

 where it was left by Newton two hundred years ago. 

 The " Principia" concludes with these words — 



"Rationem vero harum Gravitatis proprietatum ex 

 Ph^nomenis nondum potui deducere, et Hypotheses 

 non fingo. Quicquid enim ex Phaenomenis non de- 



