196 



SCIENCE 



[N. S. Vol. XXXVIII. No. 971 



Dr. Thresh makes occasional reference to 

 permutit for purposes of water softening and 

 recommends its use where the quantity of 

 water to be treated is not large. This sub- 

 stance is coming into vogue both in this coun- 

 try and in Europe. By its use carbonates and 

 sulphates of soda are substituted for the corre- 

 sponding salts of lime and magnesia. 



In discussing lead poisoning it is said that 

 " no water acts upon lead unless both carbon 

 dioxide and oxygen are present. It seems 

 probable that when carbonic acid is in a cer- 

 tain excess a solvent action is exerted, whereas 

 when oxygen is in excess the action is erosive." 



The author's treatment of the biology of 

 water is somewhat less detailed than that of 

 its chemistry, but some experiences are related 

 by him which are of interest, as, for example, 

 the effect which the process of water soften- 

 ing has in reducing the number of bacteria in 

 water. The bacteriological discussion is ma- 

 terially strengthened by quotations from Dr. 

 Houston's answers to two specific questions, 

 namely, " What bacteriological proof would 

 you consider conclusive as to the pollution of 

 a water with sewage, or manurial matter, and 

 what bacteriological proof would you consider 

 conclusive that a water is free from such pol- 

 lution or so free that it is safe for drinking 

 purposes " ? The answers to these questions 

 can not be stated in a few words, but Dr. 

 Houston apparently regards a water which 

 never contains B. coli in 100 c.c. as safe for 

 drinking; a water which contains B. coli in 

 100 c.c. in less than half the number of sam- 

 ples examined as probably reasonably safe; 

 but a water which contains B. coli in 100 c.c. 

 in a majority of samples is one to be viewed 

 with some degree of disfavor. Waters con- 

 taining B. coli in smaller amounts in a ma- 

 jority of samples can not perhaps with abso- 

 lute certainty be classed as sewage polluted, 

 but the presumptive evidence increases to a 

 more than proportional extent as a 10, a 1 

 and a 0.1 c.c. standard is infringed. Dr. 

 Houston's standards appear to be somewhat 

 more strict than those commonly discussed in 

 this country. 



The section of the book which describes in 



detail the mineral constituents of the alkaline 

 waters of the London basin is interesting to 

 analysts. More than four hundred of these 

 analyses are given in detail. 



In regard to the methods of analysis little 

 need be said. They do not differ materially 

 from those described in the first edition of the 

 book and represent the ordinary English 

 practise. 



George 0. Whipple 



Haevaed Univeesity 



Herhals, their Origin and Evolution. A 

 chapter in the History of Botany. 1470- 

 1670. By Agnes Aeber. Cambridge, the 

 University Press. 1912. Octavo. Pp. 

 xviii + 253. 



The reason for writing this book is well 

 stated by the author in her preface as follows: 

 " My excuse must be that many of the best 

 herbals, especially the earlier ones, are not 

 easily accessible, and after experiencing keen 

 delight from them myself, I have felt that some 

 account of these works, in connection with re- 

 productions of typical illustrations, might be 

 of interest to others." A little later she says 

 more specifically : " The main object of the 

 present book is to trace in outline the evolu- 

 tion of the printed herial in Europe between 

 the years 1470 and 1670; primarily from a 

 botanical, and secondarily from an artistic, 

 standpoint." 



In carrying out this object the author di- 

 vides her book into nine chapters, whose head- 

 ings will give a fair idea of its scope, as fol- 

 lows: I. The Early History of Botany (9 

 pages) ; II. The Earliest Printed Herbals (23 

 pages) ; HI. The Early History of Herbals in 

 England (12 pages) ; IV. The Botanical 

 Renaissance of the Sixteenth and Seventeenth 

 Centuries (72 pages) ; V. The Evolution of 

 the Art of Plant Description (15 pages) ; VI. 

 The Evolution of Plant Classification (20 

 pages) ; VII. The Evolution of the Art of 

 Botanical Illustration (50 pages) ; VIII. The 

 Doctrine of Signatures, and Astrological Bot- 

 any (17 pages) ; IX. Conclusions (6 pages). 

 In addition there are two appendices, I., con- 

 taining a Chronological List of the Principal 



