7 io SCIENCE PROGRESS 



The question of isotopes naturally arises here and there. Thorium is thus 

 chemically identical with ionium, the parent of radium (p. 253) ; the end product 

 of disintegration in the thorium series may possibly be an isotope of lead (p. 107). 

 Mr. Levy brings the inquiry as to whether this isotope or bismuth arises down to 

 a paper by Soddy and Hyman in 1914 ; but he is naturally unable to include the 

 work of Holmes and Lawson in December of that year. These authors conclude 

 {Phil. Mag, vol. xxviii. p. 840) that uranium passes into a stable isotope of lead, 

 while the end product of thorium is unstable, and does not accumulate in geological 

 time. 



The penultimate vowels of eudialyte and eucolite have got mixed on pp. 14 and 

 15;" eucolyte ' ; appears on p. 50, where eudialyte is spelled correctly ; but otherwise 

 slips of any kind seem extremely rare in Mr. Levy's excellently printed manual. 

 Lavenite (pp. 19 and 51) should be Lavenite or Lovenite. M. Urbain is respon- 

 sible for the spelling of Lutecium (p 205), which has stood the test of seven years 

 in this French but unclassical form. It is curious that two of the old ways of 

 dealing with Lutetia introduced a " c," but not where modern Parisians place it. 



In conclusion, we know of no book that so well covers the field selected by 

 Mr. Levy. 



Grenville A. J. Cole. 



PALEONTOLOGY 



An Introduction to the Study of Fossils (Plants and Animals). By Hervey 

 Woodburn Shimer, A.M., P.H.D. [Pp. xiv 4- 450, with 175 illustrations.] 

 (London : Macmillan & Co., Ltd. Price 10s. net.) 



It is somewhat surprising to learn from the preface of this well-illustrated little 

 volume that the students attending the author's palaaontological lectures at the 

 Massachusetts Institute of Technology too often regard fossils "merely as bits of 

 stone, differing only in form from the rocks in which they are embedded," and that 

 they also fail to realise that these same fossils contain in themselves evidence of 

 the former existence of a more or less unbroken chain connecting the animals 

 and plants of to-day with those of long past epochs of the earth's history. To 

 remedy this state of affairs, and at the same time to awaken a real interest in 

 palaeontology, Prof. Shimer has come to the conclusion that the best method is 

 thoroughly to explain the general structure of the chief groups of living plants and 

 animals, and then to show the extent of our knowledge of the extinct representa- 

 tives of each. The results of such a method of teaching are embodied in the 

 present volume, which may be regarded as a botanical and zoological text-book 

 supplemented by concise reviews of the past history of each group. In the 

 relatively large amount of space devoted to living forms and the condensation of 

 the palaeontological aspect of the subject, the work appears, indeed, to be unique ; 

 and the only question is whether this plan has not been carried to excess. 



Be this as it may, the general treatment of the subject is excellent, albeit from 

 an American point of view, which may render the work less acceptable to English 

 students than would otherwise be the case, since many of the geological formations 

 and horizons are referred to by unfamiliar local names without any indication of 

 their European equivalents. 



The volume commences with the lowest plants and ends with the highest 

 animals ; and it is satisfactory to note that in referring to the Piltdown fossil man 

 (Roanthropus dawsoni) in his concluding pages the author is thoroughly up to date. 

 In a few instances, however, this can scarcely be said to be the case. On p. 378, 

 for example, we are told that there are only two existing genera of egg-laying 



