Notices respecting New Books. 709 



the blemishes which disfigure the book, and which could easily be 

 removed in a future edition, a demand for which is certain to arise. 



In the introductory chapter on "Fundamental Physical and 

 Chemical Conceptions " the treatment of electrical units is extremely 

 slovenly. It is a pity that the translator has not adopted the terms 

 " resistance," " resistivity," " conductance " and " conductivity " 

 in the meanings now^ generally attached to them, and prefers to 

 use " specific resistance " etc. On p. 5, it is stated that " the term 

 1 potential difference ' is frequently used in place of electromotive 

 force " — a statement which, alas ! is only too true, but true by reason 

 of the very general ignorance w T hich refuses to recognize the essential 

 difference between the two terms. An exceptionally bad example 

 of negligence is to be found on p. 6, where we come across the 

 following two statements : " The difference of the potentials at two 

 points is called the potential difference or electromotive force, and 

 is that force, which tends to make the electricity pass from one point 

 to the other " ; and lower down, " the potential corresponds, in a 

 certain sense, to work " (the italics in both cases are ours). Such 

 crude and, to a learner, extremely confusing statements might be 

 excused in a popular exposition of a difficult subject ; in a serious 

 scientific text-book they are intolerable. On p. 11, the horse-power 

 is stated to be equivalent to 75 kilogramme-metres per sec. ; this 

 is true of the Continental, but not of the British horse-power, which 

 is about 1-36 per cent, larger. On p. 124, the E.M.F, of the Clark 

 cell is wrongly given as 1*438 volts at 15°. On p. 114, the author 

 adopts the method commonly followed by advocates of the dissociation 

 theory, and boldly states that the very smallest E.M.F. is sufficient 

 to produce chemical decomposition. " This fact," it is added, " was 

 proved by Buff with currents so small that it was only after months 

 that a cubic centimetre of explosive mixture was obtained." There 

 is here clearly a confusion of E.M.F. and current. We are not 

 aware of any perfectly trustworthy experiments which have shown 

 that any E.M.F., however small, is capable of evolving an explosive 

 mixture of hydrogen and oxygen from acidulated water. It is the 

 fashion, with many electrocbemists, entirely to neglect considera- 

 tions of energy in dealing with this matter. 



We have taken up so much space in pointing out some of the 

 more important errors in the book, that its excellences must be but 

 briefly referred to. Where the author is on more purely chemical 

 grouud his exposition is admirably clear and to the point. An 

 immense number of references are given to original sources of infor- 

 mation, and there is a useful index at the end of the book. 



Meteor ologisclie Oplik. Von J. M. Pernter, Professor an der K. K. 



Universitat and Director der K. K. Cent rata nstalt far Meteorologie 



mid Erdmagnetismus. Mit zahlreichen Textfiguren. II. 



Abschnitt. Wien und Leipzig : Wilhelm Braumiiller. 1902. 



Pp. 55-212. 

 Some time ago we had occasion to review briefly the first part of 

 this excellent and comprehensive treatise by Professor Pernter. 



Phil Mag. S. b\ Vol. 5. No. 30. June 1903. 3 B 



