536 



NA TURE 



[September 27. 1906 



statistics, Mr. Johnstone's severe criticism rather 

 " misses fire " at present, when definite steps have 

 been taken to improve them. It is difficult to see 

 how he can have read the report of the inter-depart- 

 mental committee of 1902, in which the recommend- 

 ations for improvement — which have since been largely 

 carried out — were made, and yet say of that report 

 that " it left the question of statistics in almost exactly 

 the same state as it was." 



In the second part of this book the life-histories 

 of fishes are dealt with in a chapter of twenty-five 

 pages of large type, and necessarily very briefly. In 

 another chapter, on the metabolism of the sea, an 

 account is given of the work of Hensen and Brandt 

 in regard to the quantitative estimation of the re- 

 sources of the sea. There are also important and 

 well-reasoned chapters on the impoverishment of the 

 grounds, the destruction of immature fish, and marine 

 pisciculture. 



The following contribution to the discussion of that 

 perennial puzzle, "What is over-fishing?" may be 

 worth quoting : — 



" If a boat (either steam trawler or smack) catches 

 fewer fish in the course of the year, it can mean 

 nothing else than this, that on the portion of the 

 sea-botto)n swept by her trawl-net there are jevoer 

 fish noiv than was formerly the case, that is, the 

 density of fish per unit of area in the North Sea fish- 

 ing grounds is less than it was thirty years ago. 

 This is a real impoverishment of the fishing grounds." 



The author sums up the present situation as re- 

 gards the relation of scientific research to legislation 

 in the following words : — 



"It would appear then that we are not yet pre- 

 pared to give thoroughly convincing reasons for the 

 adoption of legislative restrictions on those modes of 

 fishing in which small fishes are destroyed to a notable 

 extent. At the same time there can be no doubt that 

 what we do know of the life-histories of fishes does 

 justify us in recommending the adoption, as a ten- 

 tative measure, of some of the remedies proposed — 

 say the imposition of size-limits on the fishes landed 

 in certain districts," &c. , but he thinks that on the 

 whole "it is better to press for investigation on a 

 much more adequate scale than has hitherto been con- 

 templated before recommending any drastic change in 

 the fishery laws." 



Students of fishery problems will be familiar with 

 most of the arguments and criticisms in this book. 

 These have appeared before in one form or another, 

 but have never been more incisively stated than in the 

 present volume. 



AN ENCYCLOPEDIA OF PHYSICS. 

 Handbuch der Physik. By Dr. A. Winkelmann. 

 Zweite Auflage. Dritter Band, Erste Halfte : Warme, 

 pp. viii-l-s36; Vierter Band, Zweite Halfte: Elec- 

 trizitat und Magnetismus, I., pp. xiv and 385-1014; 

 Sechster Band, Zweite Halfte: Optik, pp. xii-t- 

 1404. Illustrated. (Leipzig : Barth.) Prices 16, 

 20, and 30 marks. 



PORTIONS of the second edition of this well- 

 known handbook have already appeared and 

 been noticed in these columns. Tlie characteristic of 

 the treatise is that each part is written by a specialist 

 NO. 1926, VOL. 74] 



(under the general editorship of Dr. Winkelmann), 

 and consequently it partakes of the nature of an 

 encyclopaedia. 



In the heat part appear the following sections : — 

 thermometry (Profs. Fernet and ^Vinkelmann) ; 

 expansion of solid bodies, liquids and gases, thermo- 

 electric and electric resistance, measurement of 

 temperature, specific heat (Winkelmann); thermal 

 radiation and conductivity (Graetz). Throughout 

 there is carried out a very complete system of refer- 

 ences to original sources, with critical comments. 

 This is certainly very well done in general ; but in the 

 account of constant pressure gas thermometers we 

 look in vain for any reference to the thermometer of 

 Prof. Callendar, and discover no recognition of the 

 work of the same experimentalist in the develop- 

 ment of methods of temperature determination based 

 upon the measurement of electrical resistance. We 

 presume that it is intended to recur to this subject in 

 some other portion of this voluminous treatise. 



In the electrical part appear the following 

 sections : — electrical conductivity of electrolytes, by 

 Dr. R. Luther; electricity and gases (ionisation and 

 electrification, characteristics of the electrical current, 

 migration of ions, kathode and canal rays, forces on 

 ions, thermal, chemical, and optical actions), by J. 

 Stark ; radio-activity, by J. Stark ; atmospheric elec- 

 tricity, by H. Gerdien ; thermoelectricity, by Dr. F. 

 Braun ; thermal effects of currents, by M. Cantor; 

 Pyro- and piezo-electricity, by Dr. F. Pockels ; theory 

 of the galvanic cell, by M. Cantor ; electrolysis and 

 migration of ions, by R. Luther ; electrical endosmose 

 and convection currents, by L. Graetz ; galvanic 

 polarisation and accumulators, by M. Cantor. 



From this summary it will be seen that many of 

 the sections relate to subjects in which there has been 

 a tremendous amount of work done in recent years. 

 The subject of radio-activity has, indeed, been 

 originated since the previous edition appeared, and 

 so rapidly is progress taking place in our knowledge 

 of this subject that it may be considered a moot 

 point as to what extent it is advisable to introduce 

 such quickly changing matter into a volume which has 

 the stability that a treatise of this kind necessarily 

 possesses. The references extend into the year 1904 ; 

 but even so it is impossible to praise this section as 

 representing the present state of knowledge. The 

 best that can be said is that there is not much re- 

 corded which is now known to be untrue. We think 

 this is much as it should be. An encyclopsedia should 

 contain little which has not been sifted and sifted 

 again until there is little doubt of it being an estab- 

 lished fact. To more protean volumes should the 

 task be left of pourtraying the latest phases of any 

 department of knowledge. 



These remarks apply — though perhaps not so com- 

 pletely — to other sections of the volume. The subject- 

 matters happen throughout to be those in connection 

 with which development is now most pronounced; 

 but at the worst we have here a magnificent account 

 of the branches of physics named above. 



The optical portion is probably of more stable 

 character than the rest, although here also have 



