miu'.k i<). tgi8 



NATURE 



45 



appears that this coastal flora has a predominant 

 m ter, bul ih. it about one-half oi 

 the European species ma) also occur in coldei 

 seas; and, further, that diatom-life is most abun- 

 on the south-west coast The author also 

 gives a synopsis showing the association oi th< 

 genera and species ol diatoms with the various 



genera Oi seaweeds. 



The gn ati i pan dl t li« - book (p. 395 to the end) 

 : ..led study oi the muss flora 

 ..I the island, based mainly on Mr. Hesselbo's own 

 , , .lie, lions and investigations. This comprises a 

 systematic lisi with full notes on tin- distribution 

 of the spe< us mentioned, and including ninety- 

 three liverworts, twenty sphagna, and 326 true 

 mosses. A full account of the Bryophyte com- 

 munities follows; first the lowland formations, .mil 

 secondly tin- vegetation of mountain heights. 

 Mosses pla\ a very important part in the plant- 

 covering ol Ireland, occurring either as an 

 ■1.1] component oi practically all the plant 

 associations, and often in far greater numbers as 

 end individuals than do the higher 

 plants; or .is distinct Bryophyte associations from 



which other plants are entirely absent, or in which 



they occur onLj as a subordinate component. 'The 

 lowland formations are classified as littoral, hydro- 

 philous or wet-soil, mesophilous, xerophilous 

 (heaths), the vegetation of the rocks, and the vege- 

 tation of the lax a-lields. The hydrophilous afford 

 the greatest variety, the formations varying with 

 the character of the water or soil; especially in- 

 teresting are those of the hot springs, which the 

 libes in some detail. A number of 

 ssful photographic reproductions illustrate 

 prominence of the mosses in the Iceland flora. 



The Main Currents of Zoology. By Prof. W. A. 



Lory. Pp. vii+2,16. (New York.-: Henry Holt 



and Co., igrS. 1 

 The aim of this book is to explain to the student 

 and to the general reader what have been the 

 main movements in the development of zoology. 

 In the nineteenth century, with which the author 

 begins, the outstanding biological advances were 

 discovery of protoplasm, the formulation of 

 1 U-theory, the establishment of the doctrine 

 of evolution, the rise oi bacteriology, and the 



beginning of the experimental study of heredity. 

 \1tc1 interesting chapters on taxonomy and Lin- 

 naeus, on comparative anatomy and Cuvier, on 

 embryology and \ on 11. mi. on physiology and 

 Claude Bernard, the author indicates what seem 

 To him to lie the five chief pathways — structural 

 zoology, systematic zoology, general physio- 

 logy, experimental zoology, and philosophical 

 zoology. This does not seem very satisfactory, 

 for "systematic zoologj " is taken to include 

 classification (which belongs to morphology), 

 ecology and study of habits (whi<*h belong'- to 

 physiology); and "experimental zoology " is, 



o'f. 1 .o< \ says, "more a method of general 

 application than a subdivision." 



\ chapter on insects illustrates a very charac- 

 teristic modern current, the study of the carriers 



XO. 2551, VOL. I02] 



of important disease-producing organisms, such 

 as those causing malaria and sleeping sick 



1 lnii follows a terse bul i lear exposition of 



theories of evolution. A chapter is devoted to 

 a 1 onsideration of the di leading to vac- 



cination and to the use oi ana?sthetics, with 

 emphasis on \Y. T. (i. Morton's work (1846) in 

 connection with ether. "The ten foremost men 

 of zoological history" are (alter \ristotle) 

 Harvey, Malpighi, Linnaeus, Cuvier, von Baer, 

 |uli. nines Mnllei, 1'asleur, Darwin, Max Schultze, 

 and Mendel. The study ends with an estimate 

 of the contributions to zoology made by different 

 nations, and with an emphasis on the 

 national character of science. 



I line is .1 eppious, well-arranged bibliog 

 and students will also welcome the serii - 



photographs of great zoologists. Prof. Locy is 

 beyond question right that the educational value 

 of a science is greatly enhanced if the historical 

 selling is made clear, and towards that end his 

 book will be found thoroughly effective. 



J. A. T. 

 A Primer of Engineering Science. By E. S. 

 Andrews. Part i. ( " First Steps in Applied 

 Mechanics." Part ii., " First Steps in Heat 

 and Heat Engines." Pp. ix +95 + 67. (Lon- 

 don : James Selwyn and Co., 1918.) Price 

 35. g.i. net. 

 Both parts of this book are bound in one volume. 

 Part i. contains chapters dealing with forces, 

 moments, work, power, energy, machines, various 

 types of mechanism, friction, stress and strain. 

 The matter in this part is taken from the author's 

 "Introduction to Applied Mechanics," which was 

 reviewed in Nature of January 20, 1916. The 

 experimental work described in this part is weak. 

 Six experiments in all are described; the first three 

 only are numbered. Judging from the use made 

 of spring balances in two of the experiments, these 

 appliances have no weight. Part ii. is new, and 

 consists of five chapters dealing with types of heat 

 engines, measurement of heat energy, properties 

 of steam, expansion, indicator diagrams, and the 

 transmission of heat. There are a summary of the 

 contents at the end of each chapter, and also some 

 exercises to be worked by the student. Ten ex- 

 periments are described in this part. No table of 

 the properties of steam is given; a graph is in- 

 cluded, but stops at 100 lb. per square inch ; since 

 it is reproduced to a small scale, accurate readings 

 cannot be taken from it. There is evidence of 

 haste in the compilation. On p. 2 the piston ring 

 is described as a "junk" ring-; Fig. 6 (c) on p. 

 is wrongly arranged; it is stated on p. 39 that 

 Boyle discovered his law in 1862 ; on p. 50 a. di - 

 gram traced by an indicator is described as " a 

 diagram of resultant force or effort upon a body." 

 Some of the diagrams are badly reproduced, this 

 being owing to the quality of paper used. Con- 

 sidering the book as a whole, the young student 

 will find some parts interesting and helpful ; other 

 parts are treated unsuitably, and a considerable 

 an of supplementary matter will have to be 

 supplied by his teacher. 



