June 7, 1894] 



NA TURE 



12 



carry away a very unfavourable impression of them if he 

 confined his attention to this part of the book. The fol- 

 lowing portions, which treat of the application of the 

 method to ores, alloys, rocks, &c., are much more satis- 

 factory, and contain information of great value to the 

 metallurgist, petrologist, and others. 



After all, micro-chemical analysis is only in its infancy, 

 and, as the author points out, the present work will 

 doubtless prove to be a mere outline compared with the 

 manuals which will be published twenty years hence, 

 "when the advantages of micro-chemical analysis will be 

 understood everywhere, when its appliances will be fully 

 developed, when difficulties have been surmounted, and 

 obscurities have been cleared up. ' Meanwhile it is to 

 be hoped that the publication of this small but ex- 

 tremely valuable little volume will have the effect of 

 largely increasing the number of those who use micro- 

 chemical methods in this country. 



OUR BOOK SHELF. 



Practical Botany for Beginners. By F. O. Bower. 

 (Macmillan and Co., 1894.) 



Prof. Bower's well-known "Practical Botany" has 

 won for itself universal recognition as forming an indis- 

 pensable adjunct to the botanical laboratory. But with 

 its increasing popularity the size and scope of the 

 volume also advanced, and at the present time, though 

 it is invaluable to the student with sufficient time at his 

 command, it is somewhat bulky for the large class of 

 persons who, from various circumstances, require a 

 more elementary acquaintance with the types they 

 investigate. 



It is for these that the " Practical Botany for Be- 

 ;:;inners " has been designed, and it will certainly prove of 

 _;reat service. Although the book is of smaller dimen- 

 sions than the larger work just referred to, it is still con- 

 ducted on the same lines. The text, so far as it goes, is 

 for the most part similar, and the reduction in size is pro- 

 vided for by the use of smaller type, and by the omission 

 of many subsidiary descriptions which had been intro- 

 duced for purposes of comparison. 



Like all good introductory books, it assumes no 

 previous knowledge in the department to which it re- 

 lates, and thus the student is enabled to begin really at 

 the beginning. It will, however, be his own fault if he is 

 not in possession of a very creditable amount of sound 

 knowledge by the time he has worked through the 

 volume. For those who are unable to go through the 

 more extended course, a better book than the present 

 one could not be recommended. 



Simple E.xperiments for Science Teaching. By John A. 

 Bower. (London : Society for Promoting Christian 

 Knowledge, 1S94.) 



Teachers of science in elementary schools now live in 

 halcyon days. Time was when books containing courses 

 of experiments suitable for teachmg the young idea the 

 science of common things were hard to find, and they who 

 desired to impart such instruction had to prepare their 

 own sequence of lessons. But the examinations of the 

 Science and Art Department and similar bodies have 

 changed all that. There are now numerous primers for 

 all branches of elementary science, some good, many 

 inditlerent, and a few bad. Teachers are no longer under 

 the necessity of exercising the facultv of originality in 

 devising experiments for class demonstration, for the 

 work is done for them, and frequently done well, by the 

 much-maligned text-book writer. Possibly the mental 

 atrophy thus brought about is not desirable, but there is 



NO. I 2S4. VOL. 50] 



little doubt that the teaching has been benefited. Few of 

 the courses of elementary science in our schools and 

 colleges were truly scientific in character, and it is chiefly 

 the text-book that has improved the old stale of things 

 by giving law and order to the chaos of experiments. 



Mr. P.ower's book deserves classification with those that 

 help on the work of science. It consists of two hundred 

 experiments fully illustrating the elementary " Physics 

 and Chemistry ' division in the code for evening con- 

 tinuation schools. The experiments are well graded, 

 they are simple, they illustrate phenomena of every-day 

 life,and most of them can be performed with thehomeliest 

 things. The pupil who sees the experiments will learn 

 much ; he who does them will obtain an excellent founda- 

 tion in physical scifnce. The book is nicely printed and 

 sufficiently illustrated, and would be a very acceptable 

 present for a boy fond of finding out some of the ways of 

 nature. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond -with the writers oj, rejected 

 manuscripts intended for this or any other part o/Naturk. 

 No notice is taken of anonymous communications.'\ 



The Teeth and Civilisation. 



In a letter to Nature for May 17, on "The Teeth and 

 Civilisation," the writer advances a theory to account for the 

 great prevalence of decay of the leeth at the present day, and 

 "concludes that Dr. Wilherforce Smith's investigations show 

 that "the ancients enjoyed a perfect set of teeth till advanced 

 years, and modern savages enjoy the same blessint;." 



I have not had the opportunity of seeing Dr. Wilberforce 

 Smith's communication, but the number of cases examined in 

 this particular instance (ten Sioux Indians) would hardly he 

 sufficient to draw any conclusions from ; and even in these ten 

 cases all the teeth were not examined. I think, however, it 

 has been sufficiently proved by several careful investigations 

 that caries of the teeth is not a purely modern disease, and is 

 not entirely confined to civilised races. My father, in a com- 

 munication to the Odontological Society in 1870, brought 

 together the results of an inquiry extending over more than 

 ten years, in which he examined over 2000 skulls, including all 

 the available collections in Great Britain, and his conclusions 

 as to the prevalence of dental caries differ very considerably 

 from those of the writer of this letter. 



Among thirtv-six skulls of ancient Egyptians he found caries 

 in fifteen (41 '66 per cent.), in seventy six Anglo-Saxon skulls 

 he found twelve cases (15-78 per cent.), among 143 skulls of 

 Romano Britons there were 41 cases of caries (28-67 per cent.), 

 while among 44 miscellaneous skulls of ancient Britons 20-45 

 per cent, showed carious teeth. Several other collections gave 

 similar results. 



Again, with regard to savage races — among the Tasnianians 

 27-7 per cent, of caries was found, among native Australians 

 2045 per cent., among East African skulls 24-24 per cent, and 

 among those of West African natives 27 96. 



Similar results were ol>tained on the examination of skulls 

 of many other races, but I think I have quoted fitjures sufficient 

 to prove that caries is not confined to civilised races or to 

 modern times. 



It is quite comprehensible that excessive nerve strain, 

 especially by aflecling vascular supply, may lead to imperfect 

 nutrition during the development of the teeth, and we know 

 that the diseases of early childhood have a very marked effect 

 upon tooth structure, indicated by the ridged and defective 

 leeth so frequently seen, and it seems quite possible that loo 

 early stimulus of the brain in childhood may have a similar 

 effect on forming teeth. It is very difficult, however, to under- 

 stand how nerve strain can have any direct effect upon fu'.ly 

 famed teeth, and we should, I think, look for the explanation 

 of the cases referred to in some vitiated condition of the fluids 

 of the mouth, caused by the depressed condition of health so 

 common amongst hospital nurses. 



There is little doubt ihat an open-air life and healthy 



