2 20 



NA TURE 



[July 6, J893 



destroyed ; this fact explains the absence of this and 

 other microbes in the air at sea — the latter containing an 

 appreciable amount of ozone." Innumerable experiments 

 have surely proved that the absence of microbes in sea- 

 air would be anticipated on mechanical grounds quite 

 irrespectively of the possible subsidiary effect of ozone. 



We believe that Dr. Griffiths is primarily a chemist, 

 and a number of pages in this work are devoted to the 

 chemical products elaborated by microorganisms ; in 

 this connection we are informed that yeasts secrete a 

 soluble enzyme which converts maltose into dextrose and 

 levulose (sic), nor is it easy to believe that this is a lapsus 

 plums, for the equation is given with the explanatory 

 names beneath the formula, thus 



C12H22O11+ H2O = QHijOc + QH,.206. 



[maltose] [dextiose] [levulose] 



Dr. Griffiths devotes a number of pages to the subject of 

 hydrophobia, but in connection with the hitherto undis- 

 covered vital cause of this malady we hardly think that 

 either the public or the scientific world will feel much 

 interest in the author's statement that he has "observed 

 a micrococcus in the saliva of a woman suffering from 

 hydrophobia," notwithstanding the categorical assurance 

 which follows that "this microbe does not occur in 

 healthy human saliva." 



In dealing with the much-vexed subject of the etiology 

 of pneumonia, the author refers only to the pneumococcus 

 of Friedlander which has long been regarded as an 

 ineligible candidate for the distinction of being the 

 specific cause of this disease, whilst of the far more 

 probab!e diplococcus of Frankel there is no mention 

 whatever, nor indeed of the uncertainty which surrounds 

 the entire question. 



Similarly, in connection with the bacillus of typhoid 

 fever we find no mention of the closely-allied Bacillus 

 colt communis, nor does the author appear to be 

 acquainted with any of the modern methods which have 

 been resorted to for its diagnosis, but contents himself 

 with copying a long passage from Gaffky's original paper 

 of 1886 in which the statement is made that the well- 

 known potato-test serves to distinguish this microbe from 

 all others. Indeed, the transcription of long passages 

 from the works of other authors is a striking feature in 

 this book, and inasmuch as such extracts are not printed 

 in different type, the reader must be ever on the alert for 

 the small inverted comma, in order to know whether he 

 has before him the words of Dr. Griffiths or those of 

 some more or less distinguished authority. 



We do not think that any useful purpose would be 

 served in pursuing this criticism further, nor should we 

 have referred to as many points as we have done but 

 that we have such strong reason to believe that the 

 circulation of works of this kind among some sec- 

 tions of the public is fraught with no little danger. 

 It is by no means uncommon for persons without 

 any special qualification whatever, but with plenty 

 of cheap assurance and a smattering of informa- 

 tion gleaned from semi-popular works like the one before 

 us, to perambulate the country under the auspices of 

 county councils and other equally competent bodies, and 

 to deliver discourses or even write books on sanitary 

 and hygienic subjects; so that if the sources from which 

 NO. 1236, VOL. 48] 



these retailers of third-hand knowledge draw are gi 

 vously inaccurate, it requires but little imagination 

 realise how serious may be the consequences. 



THERMOD YNA MICS. 

 Die Thermodynamik in tier C hemic. Von J. ]. \ 

 Laar. Mit einem Vorsvort von Prof. Dr. J. H. var 

 Hoff. Pp. xvi., and 196. (Amsterdam and Leip2 

 1893-) 

 ' I ""WENTY years ago the first application of 1 

 *- second law of thermodynamics to the study 

 chemical phenomena was published by Horstmann, a 

 shortly afterwards the whole subject was investigal 

 by Willard Gibbs, but in a manner so general that i 

 work failed to gain the recognition of physical chemi 

 for many years. Within the last decade, however, p 

 gress in this direction has been very rapid, and spec 

 branches or special aspects of chemical ihermcdynam 

 have received exhaustive treatment at the hands 

 van 't Hoff, Le Chatelier, Duhem, Planck, and othe 

 But if we except the novel and brilliant exposition int 

 new edition of Ostwald's " Lehrbuch der allgemein 

 Chemie," a general survey of the modern applicatio 

 of thermodynamics to chemistry has hitherto been war 

 ing, and it is to supply this want that Dr. van Laar h 

 written the present volume. 



The first half of the book is concerned with genei 

 thermodynamical principles and their application to t 

 behaviour of gases and saturated vapours. The devi 

 tions from the laws of perfect gases are considered ve 

 fully — indeed, at inordinate length. As Prof, van 't Hi 

 says in his preface, the work is alternately text-book ai 

 memoir. Now, while this method of treatment ni; 

 have its advantages, it entails an utter absence of balan 

 between the various parts of the work It appears, f 

 instance, out of all proportion to devote a fifteenth pa 

 of the whole book to the discussion of the formula f 

 the vapour pressure of a liquid. After making his w: 

 through thirteen pages of infinite series, differenti 

 equations, and determinants, the student finds th; 

 when judiciously modified, van der Waals's equation cj 

 be made to express exactly the relationship between tl 

 temperature and pressure of a vapour in contact with i 

 liquid — a result (to the chemist, at least) quite incon 

 mensurate with the trouble involved in arriving at it. 



It is the second half of the work which is of speci: 

 interest to students of physical chemistry. Beginnir 

 with the fundamental entropy principle of Gibbs, tl 

 author develops the various equilibrium equation 

 and gives a general proof of the important relatio 

 rflog KA/T = Q/RT^. Then come applications to concrel 

 cases of dissociation and balanced action. The " tempi 

 rature of transformation " of phases of constant con 

 position and the " triple point " are next fully discussec 

 and the last portion of the book is occupied with th 

 behaviour of dilute solutions. Here the new theories ( 

 osmotic pressure and electrolytic dissociation areviewe 

 from the thermodynamical standpoint, many importar 

 constants being calculated afresh. The depression of th 

 freezing point and of the vapour pressure in solutions, a 

 well as the question of affinity constants, all receive ad< 



