January 23, 19 13] 



NATURE 



i67 



(5) The question of the origin of megalithic 

 monuments and of the race by whom they were 

 constructed has acquired fresh importance from 

 the discussion, at the recent meeting of the 

 British Association at Dundee, of the theories 

 advanced by Prof. G. Elliot Smith, who 

 attributes them to influence from Egypt, 

 where he assumes that the invention of 

 copper led to the use of carved stone. Mr. 

 Peet's method in the present book is to give a 

 summary account of megalithic monuments 

 throughout the world, to which he adds some 

 cautious, well-considered speculations on their 

 origin and diffusion. He fully recognises the 

 difficulty, in the present state of our knowledge, 

 of deciding the centre from which they were de- 

 rived. He suggests that the idea of the rock- 

 tomb was brought into the megalithic area by the 

 builders of the monuments, that it did not result 

 from contact with the eastern Mediterranean, 

 and that there is no direct connection between 

 the corridor tombs of the megalithic countries and 

 the great Tholoi of Crete and the Greek mainland. 

 The book may be safely recommended as a 

 cautious summary of a most difficult problem. 



RECENT BOOKS ON PHYSICAL SUBJECTS. 



(i) Elements and Electrons. By Sir W. Ramsay, 

 K.C.B., F.R.S. Pp. ix+173. (London and 

 New York : Harper and Brothers, 1912.) Price 

 25. 6d. net. (Harper's Library of Living 

 Thought.) 



(2) Radium a)7d Radioactivity. By A. T. Cameron. 

 Pp. 185. (London: S.P.C.K., 1912.) Price 

 2S. 6d. (Rom.ance of Science Series.) 



(3) A Handbook of Physics. By W. H. White. 

 Pp. XV + 667. (London : Methuen and Co., Ltd., 

 n.d.) Price 75. 6d. 



(4) .4 Course of Physics, Practical and Theoretical. 

 By Dr. C. H. Draper. Pp. xi-t-413. (London : 

 Blackie and Son, Ltd., 1912.) Price 45. 6d. net. 



(5) La Thdorie des Ions et I' Electrolyse. 

 Deuxi^me Edition. By A. HoUard. Pp. vii 4- 

 220. (Paris: Gauthier-Villars, 1912.) Price 

 5 francs. 



(6) Lehrbuch der Optik. Dritte erweiterte Auflage. 

 By Dr. Paul Drude. Herausgegeben von Dr. E. 

 Gehrcke. Pp. xvi-i-548. (Leipzig: S. Hirzel, 

 1912.) Price 12 marks. 



(7) Electricity and Its Practical Applications. By 

 Prof. M. Maclean. Pp. xiv4-492. (London: 

 Blackie and Son, Ltd., n.d.) Price 105. 6d. net. 



(i) TT need scarcely be stated that a popular 



\_ treatise from the pen of Sir William 



Ramsay is sure to be of absorbing interest. This 



is particularly the case with the present volume, 



XO. 2256, VOL. 90] 



with the subject of which the author's name is 

 so intimately associated. The various stages in 

 the development of chemistry, and later of radio- 

 activity, are sketched in a manner quite delightful, 

 and although the treatment of the mechanics in- 

 volved may be regarded by some as rather loose, 

 it is only in a few instances that this objection 

 can be raised, and it should be remembered that, 

 after all, the readers will not all be strict mathe- 

 maticians. 



The principal chapters are those which deal with 

 Dalton's atomic theory, molecular weights, the 

 periodic table, molecules — invisible and visible — 

 electrons, radioactivity and transmutation. Prob- 

 ably the last of these is that which will invoke the 

 greatest interest. It is common knowledge that 

 Sir William Ramsay's work in this field has been 

 received in some quarters with scepticism, and, of 

 course, all controversies are popular. The author 

 draws a distinction between " transmutation " and 

 "transformation," the former applying to con- 

 trolled changes as distinct from natural changes. 

 Among the reasons brought forward as indicating 

 the probable effect of corpuscular bombardment in 

 producing transmutation, it is suggested that it 

 may be due to high temperature. The " tempera- 

 ture " of rapidly moving alpha particles is cal- 

 culated upon the kinetic theory, and the number 

 obtained is enormous. 



With this view it is difficult to agree, for even 

 if we admit the validity of this calculation as repre- 

 senting the temperature of the particles them- 

 selves, it cannot be claimed that it also measures 

 the temperature of the body bombarded. But 

 apart from this, the accumulated evidence of 

 transmutation which is recorded in this chapter 

 should not be lightly dismissed, especially coming 

 as it does from the discoverer of the spontaneous 

 production of helium from radium. It may be 

 scarcely credible, because so extraordinary, but 

 it may, nevertheless, be true. 



(2) This is another little book on somewhat 

 similar lines, although, in this case, radioactivity 

 is the sole subject. The author takes the very 

 reasonable view that some knowledge of physics 

 and chemistry must be assumed in the reader, but 

 the calls on this knowledge are neither great nor 

 numerous, and will form no bar to the majority 

 of students. A straightforward and interesting 

 account of the main radioactive phenomena con- 

 stitutes the contents of the book, and the novice 

 who desires some acquaintance with this won- 

 derful new subject could not do better than 

 acquire a copy. 



(3) It is not often that one comes across a text- 

 book exhibiting so much originality as that which 

 Mr. White has recently produced. To say that 



