1 68 



NATURE 



{yune 19, 1879 



that the space at our disposal will not perniit of our fol- 

 lowing the author in these interesting discussions, and 

 we can only, in conclusion, heartily recommend the work 

 to the traveller as being admirably adapted to guide him 

 in investigating the geology of a district of extreme inte- 

 rest and great complexity, and to the student at home as 

 containing numerous facts and suggestions worthy of the 

 most thoughtful consideration. J. \V. J. 



HEALTH PRIMERS 

 Health Primers. Edited by J. Langdon Down, M.D., 

 F.R.C.P., Henry Power, M.B., F.R.C.S., J. Mortimer- 

 Granville, M.D., John Tweedy, F.R.C.S. (London : 

 Hardwicke and Bogue.) 



THE proverb that a little knowledge is a dangerous 

 thing is especially true in regard to matters con- 

 nected with health, and it might therefore be supposed 

 that the issue of a series of health primers was a thing 

 to be deprecated, as likely to do harm. But a little re- 

 flection will show that this series is intended, not to 

 impart a little knowledge, but to replace the knowledge, 

 not merely little, but confused and inaccurate, which 

 every man supposes himself to possess, by something 

 more definite and exact. Every one fancies that he 

 knows the appearances of health and disease, and that 

 he is able to decide upon the condition of those whom he 

 daily meets. Every man supposes himself able to [pro- 

 nounce that such and such a house cannot be healthy, 

 and believes that he is quite capable of judging for himself 

 how much exercise he ought to take, whether he should 

 or should not use a cold bath in the morning, and what is 

 the proper allowance of beer, wine, or spirits, either for him- 

 self or for his neighbours. Now, despite the confidence 

 with which most men will pronounce an opinion on all these 

 subjects, the data on which they would found that opinion 

 would really be very slight, and their knowledge of the 

 subject probably very imperfect and inaccurate, and, con- 

 sequently, the conclusions at which they would arrive 

 would most likely be erroneous. It is just on such sub. 

 jects as those we have mentioned that the books of this 

 series afford accurate information. The first of them, 

 " On Premature Death, its Promotion and Prevention," 

 is of a less popular character than the others, and has, 

 we think, suffered in _ consequence of its author not 

 having seen the contents of the other primers. While 

 the material it contains is very valuable, it deals, we 

 think, too much' with statistics and too little with the 

 causes of premature death which are under the control 

 of the individual, although occasionally, however, it gives 

 these also, as at p. 46, where ventilation in a hospital is 

 said to have put a stop to the convulsions from which the 

 children died in great numbers, and reduced the mortality 

 to j^ of its previous amount. But on the other hand, 

 while we learn that 6 per cent, of the total mortality from 

 all causes is due to diseases of the heart, the writer says 

 nothing of the dangers incurred in running after an 

 omnibus or in trying to catch a train. 



The primer on " Personal Appearance in Health and 

 Disease" includes the changes which the body may 

 undergo in the form and size of its bony framework, fatty 

 layer, and internal organs, as well as external colour. 

 These are given shortly and well, though the alterations 



produced artificially by tight-lacing and high-heeled and 

 tight boots might have been still more strongly insisted 

 upon and emphasised by woodcuts showing their results. 



" The House and its Surroundings " is clearly written, 

 and contains a great deal of very useful information. By 

 its aid the householder should be able to know where to 

 look for defects in drainage, ventilation, water supply, &c. 

 and thus to avoid many sources of disease, although we 

 think that the dangers of arsenical wall-papers ought per- 

 haps to have been more strongly insisted upon. 



"Baths and Bathing" discusses the physiological 

 action, varieties, and uses of baths and bathing localities, 

 both at home and abroad. It is written in a very readable 

 style, and contains both advice as to the use of baths and 

 cautions in regard to their abuse. The author warns 

 against the too heroic use of a morning tub, but forgets to 

 state how very much the chilliness which it brings on in 

 persons of languid circulation may be prevented by using 

 a bath sheet instead of a towel, so that the whole body 

 shall be covered during drying, and not chilled by the 

 exposure of the wet skin to the cold air. 



" Exercise and Training " gives a general account of 

 the changes produced in the body by muscular exertion, 

 of the food required, the general regime to be pursued, 

 and the dangers to be avoided. It is evidently written 

 by one who is familiar with the subject of which he is 

 treating. 



"Alcohol, its' Use and Abuse," deals with a very diffi- 

 cult subject, and does it well. The author is not prejudiced 

 cither for or against alcohol, and maintains that because 

 ninety-nine persons out of a hundred misuse it, it is none 

 the less true that it has a right use, this use being some- 

 times to check the current of thought and care, as well 

 as to stimulate digestion and circulation, although in 

 perfect health its use is unnecessary. 



The purpose which these primers are intended to serve 

 is a very important one, and we think that they are well 

 calculated to serve their purpose. We have pointed out 

 one or two things in which we think they might be im- 

 proved in future editions, but on the whole they are well 

 and carefully done, giving accurate information in a 

 condensed yet popular form. T. L. B. 



LETTERS TO THE EDITOR 



[The Editor does not hold h imself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that 

 is impossible othenvise to ensure the appearance even of a 

 munications containing interesting and novel facts .'] 



The Mechanical Theory of Earth-Heat 

 Noticing the assertion made in Nature, vol. xx. p. 22, __ 

 reference to Prof. Church's article in Silliman's Journal on the 

 Comstock Lode, that "the rock in the lower levels seems to 

 have a pretty uniform temperature of 130° F.," and remembering 

 what Prof. G. F. Barker, of the University of Pennsylvania, told 

 me, that on a recent visit to those mines he found that there was 

 no uniform temperature, but on the contrary, the most remark- 

 able differences, some of the higher levels being much hotter 

 than some of the lower levels — so that he came to two conclu- 

 sions : — (l) That the heat was a hot water heat, and (2) that 

 the hot waters were heated mechanically by those continuous 

 movements of the country, so plainly shown both in the mines 

 and at the surface; — it occurs to me to ask the following 

 question : — 



"s as 



