244 



NATURE 



[May 24, 19 1 7 



OVR BOOKSHELF. 

 Studies in Insect Life, and Other Essays. By 

 Dr. A. E. Shipley. Pp. ix + 338. (London: 

 T. Fisher Unwin, Ltd., 1917.) Price 105. 6d. net. 

 Ft is Dr. Shipley's gift to write scientific essays 

 artistically, using many-coloured lights from 

 reading and experience to illumine and humanise 

 hard grey facts. He has humour and a light 

 touch, and things are so interesting to himself 

 that they become interesting to us. Not that 

 we pretend to explain his style, which permits 

 of luminous, dignified discourse on lice and fleas, 

 as well as on fisheries and grouse. "Le style," 

 said Buffon, "est comme le bonheur; il vient de 

 la douceur de I'ame." 



The book, based on previously published 

 essays and lectures, has eleven chapters, dealing 

 with insects and war, honey-bees, humble-bees, 

 wasps, the depths of the sea, fisheries, Sir John 

 Murray, grouse-disease, zoology in the time of 

 Shakespeare, the revival of science in the seven- 

 teenth century, and hate. We have seen no more 

 successful rapidly drawn picture of a haunt of 

 life than is to be found in the chapter on "The 

 Romance of the Depths of the Sea." Another 

 fine picture of a very diflferent kind is that of 

 Sir John Murray. It is very interesting to have 

 Dr. Shipley's lively summary of his own investi- 

 gations on what is called "grouse-disease," of 

 which, adapting Sydney Smith, he says : " Little 

 stoppages, food pressing in the wrong place, a 

 vext duodenum, and an agitated blind-gut, and 

 there you have * grouse-disease. ' " 



In the essay on hate an exposition is given, 

 after Cannon and others, of the part the secretion 

 of the supra-renal capsules plays in " the .bodily 

 changes which occur in states of extreme pain, 

 fear, or rage, and serve to place * un enrage ' 

 in an eminently favourable state for wreaking his 

 passion on his opponent." It has been suggested 

 that the use of golden mice in connection with 

 emerods may have implied some awareness of the 

 correlation between rodents (with their fleas) and 

 bubonic plague ; Dr. Shipley wonders whether 

 the ancient Hebrews knew anything about the 

 potency of the supra-renal capsules, because they 

 were so very particular in their burnt offerings to 

 offer up "the fat upon the kidneys." We have 

 but one fault to find with this entertaining 

 volume, that it comes to an end too soon. 

 The Tutorial Chemistry. Part ii., Metals and 

 Physical Chemistry. By Dr. G. H. Bailey. 

 Edited by Dr. W. Briggs. Third edition. 

 Pp. viii + 460. (London : W. B. Clive, Univer- 

 sity Tutorial Press, Ltd., 1917.) Price 45. 6d. 

 The general character of this widely known text- 

 book was described in the review of the first 

 edition which was published in Nature for 

 April 14, 1898 (vol. Ivii., p. 559). In the present 

 issue the second half of the section of the book 

 dealing with physical chemistry has been com- 

 pletely recast by Mr. H. W. Bausor. The whole 

 text has been revised, and the pages concerned 

 with crystallography have been transferred to an 

 appendix. 



NO. 2482, VOL. 99] 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



The Stability of Lead Isotopes from Thorium. 



Since my receni letter on the subject of "thorium" 

 lead (Nature, February 15, p. 469) I have had some 

 correspondence with Dr. Arthur Holmes, who, in 

 agreement with Boltwood, had previously concluded 

 from geological evidence that lead could not be the 

 end product of thorium, because thorium minerals 

 often contain so little lead in comparison with what 

 is to be expected from their age. He pointed out that 

 the a,ge of Ceylon thorite as determined from the 

 ratio of lead to thorium was curiously anomalous. 

 Taking, as preferable, Rutherford's values for the 

 periods of uraniuin and thorium, 072 and 1-9 ( x 10^* 

 years) respectively (in the ratio of i to 2-6, instead of 

 3-2, the figure used in the previous letter), the pro- 

 portion of the thorite lead derived from the thorium 

 would be 955 per cent., and from the uranium 45 per 

 cent. The quantity of thorium lead per gram of 

 thorium would be 00062. The rate of growth would 

 be 472 X 10-^^ gram of lead per gram of thorium per 

 year, and the age of the mineral 131 million years. 

 A Ceylon pitchblende (U = 72-88 per cent., Pb = 4-65 per 

 cent.) has a ratio of lead to uranium of 0-064, giving 

 the age as 512 million years, and Dr. Holmes con- 

 siders that this is likely to be of the same geological 

 age as the thorite, and to be, pf all the Ceylon results, 

 the most trustworthy for age measurements. 



It must be remembered that there are two end 

 products of thorium, both being isotopes of lead with 

 the same atomic weight. Thorium-C, an isotope of 

 bismuth, disintegrates dually, 35 per cent, of the atoms 

 expelling first an a and then a /S ray, and 65 per cent, 

 first a j8 and then an a ray. More energy is ev'olved 

 in the latter mode than in the former, and although 

 the two isotopes have the same atomic mass and the 

 same chemical character, there may be a difference 

 in stability. From analogy with the uranium series, 

 where the same thing is true for radlum-C, except that 

 all but a minute fraction of the atoms follow the 

 second mode, it is the 65 per cent, isotope of thorium 

 lead which should further disintegrate, for it is 

 analogous to radium-D. 



On the supposition that only the 35 per cent, isotope 

 is stable enough to accumulate, the age of the mineral 

 calculated from the data given would become 375 

 million years, in nearer agreement with the pitch- 

 blende. But the most interesting point is that if we 

 take the atomic weight of the lead isotope derived 

 from thorium as 206-0, and that from thorium as 

 2080, and calculate the atomic weight of thorite lead 

 on this basis, we get the same value, 207-74, which 

 I obtained from the density, and Honigschmid obtained 

 for the atomic weight (2o7;-77). 



The question remains. What does the unstable isotope 

 change into? Clearly the rate of change must be 

 excessively slow to account for the apparentlv complete 

 decay of the radiation of thorium-C. A /3 or an a 

 ray expelled would result in the production of bismuth 

 or mercury respectively, elements of which I could 

 find no trace in the lead group separated from 20 kilos 

 of mineral. But an a and a 3 change would produce 

 thallium, which is present in the mineral in amounts 

 that sufTiCvid for chemical as well as spectroscopic' 

 identification. On this view, then, this particular lead 

 should give a feeble specific o or ^ radiation, in addi- 

 tion, of course, to that produced by other lead isotopes 

 present. Circumstances do not permit me 'to test the 



