REVIEWS 719 



The first few chapters are devoted to an account of the early discoveries 

 in Light, Electricity and Magnetism, followed by a chapter on the theories of the 

 aether in which its properties are compared with those of an elastic solid. A 

 description of the epoch-making discoveries of Faraday and the work of the 

 mathematical electricians of the middle of the nineteenth century leads up to 

 Maxwell's Electromagnetic Theory and its elaboration by later workers. A per- 

 fectly continuous narrative could not be expected in a subject consisting of at 

 least three different branches but by following up one branch through a definite 

 period of development and then returning to another, the author has produced a 

 very readable book, which preserves the interest throughout. The controversies 

 which have raged about opposing theories, such as the one-fluid and two-fluid 

 theories of electricity and the corpuscular and wave theories of light and the 

 crucial experiments devised to decide between them are told in a clear and 

 concise manner. Due importance is given to such fundamental questions as the 

 existence of a pressure due to light, the direction of the vibrations of eether 

 particles in a polarised beam relative to the plane of polarisation, anomalous 

 dispersion and the motion of the sether, their influence on the construction of 

 different theories being carefully pointed out. No statement is made or opinion 

 attributed without quotation or full reference, a feature to be highly commended 

 and the whole forms a review of this department of physical science which will 

 receive a welcome, not from the historical standpoint only but from the point of 

 view of those interested in further developments of the subject. As one reads of 

 the early wave theory of light abandoned for a century owing to its imperfections 

 and yet so much nearer the truth than the accepted corpuscular theory or as one 

 reads of Bernoulli, who in 1736 forestalled some of the ideas of Maxwell, one is 

 compelled to wonder whether any of the dead and abandoned theories of the past 

 will yet rise again as our knowledge advances and, corrected, displace those 

 we now accept. Certain it is that no claim can be made for any theory, including 

 those now generally accepted, that it is a complete explanation of the known 

 experimental facts. 



One suggestion only we have to make. The value of the book would have 

 been enhanced if the author had concluded his detailed history with a short 

 summary, free from the theory and proofs previously fully dealt with, giving our 

 present conceptions of the aether and electricity, with a statement of the points 

 on which they are imperfect. Such a crystallisation of present opinion may give 

 a misleading appearance of finality but it is preferable to a diff"use ending in which 

 accounts of the present state of thought on different phenomena are scattered over 

 many pages; an ending which is not apt to complete that feeling of enjoyment 

 with which a reader should lay down a work of this character. Apart from this 

 minor point, the book is one in all respects to be commended and will form a 

 valuable addition to our scanty literature on the History of Physics. 



H, Moss. 



Induced Cell-Division and Cancer. The Isolation of the Chemical Causes of 

 Normal and Augmented Asymetrical Human Cell-Division. By Hugh 

 Campbell Ross, M.R.C.S., L.R.C.P. [Pp. 291.] (London: John Murray, 

 1910. Price \2s. net.) 



Mr. H. C. Ross claims to have discovered that practically the whole of the 

 existing descriptions of the phenomena connected with the multiplication of 

 animal cells are misinterpretations of facts, due to faulty methods of investigation. 



