3° 



NATURE 



[March 



1913 



OUR BOOKSHELF. 

 Miners' Nystagmus : its Causes and Prevention. 

 By Dr. T. Lister Llewellyn. With a preface by 

 Prof. J. S. Haldane, F.R.S., and a legal appen- 

 dix by Douglas Knocker. Pp. xix-ri58 + 

 plates. (London: The Colliery Guardian Co., 

 Ltd., 1912.) 

 Mixers' nystagmus is a disease which incapaci- 

 tates a large number of coalminers, and is esti- 

 mated by Dr. Lister Llewellyn to cost the country 

 ioo,oooZ. a year. It is characterised by rapid 

 involuntary movements of the eyes, associated 

 with defect of vision, photophobia, and night- 

 blindness. Many theories have been brought 

 forward to account for the disease. Of these the 

 myopathic theory has been most supported in 

 England, chiefly owing to the writings of the late 

 Mr. Simeon Snell, of Sheffield. The work is 

 carried on in constrained positions, often necessi- 

 tating prolonged exercise of the extra-ocular 

 muscles in an abnormal manner. It is now gener- 

 ally admitted that undue weight was attached to 

 this factor, and attention has been specially 

 directed to the view that the real cause is the poor 

 illumination, a suggestion first made by Romiec, 

 who, however, thought that excessive accommo- 

 dation was an essential concomitant. 



Dr. Llewellyn, as a former medical officer to a 

 South Wales coal and iron company and as 

 Tyndall Research Mining Student of the Royal 

 Society, has had excellent opportunities for investi- 

 gating the disease. He has used his opportuni- 

 ties to the full, and his work is a model of what 

 such a research should be. He has shown conclu- 

 sively that miners' nystagmus is practically limited 

 to coal mines in which safety lamps are used, those 

 in which naked candles are employed being exempt 

 except for cases which have been transferred from 

 safety-lamp mines. He has made exhaustive in- 

 quiries into the conditions of work and the illu- 

 mination at the coal face. The estimations of 

 illumination appear to have been made with great 

 care and accuracy, and the same may be said of 

 the clinical investigations. In addition to his own 

 researches, his book contains an admirable 

 resume 1 of the opinions and work of previous 

 writers on the subject. The criticisms are judicial 

 in tone, and the exposition of his own views allows 

 the facts and arguments to carry conviction with- 

 out undue stress. The work is of interest not onlv 

 !" those specially associated with the mining 

 industry, but also to the physician and physiolo- 

 gist. We consider that Dr. 'Llewellyn has accom- 

 plished a difficult task with distinguished success. 

 Catalogue of the Lepidoptera Phalaenae in the 

 British Museum. Vol. xii. : Catalogue of the 

 Noctuidae in the Collection of the British 

 Museum. By Sir George F. Hampson, Bart. 

 Pp. xiii + 626. (London: Printed by Order of 

 the Trustees, 1913.) Price 175. 6d. 

 The subject of this volume of the " Catalogue of 

 Moths " is the classification of part of the Noctuid 

 subfamily Catocalinae. The remaining portion of 

 the subfamily, together with the small subfamilies 

 NO. 2263, VOL. 91] 



Mominae and Phytomatrinae, will appear in vol. 

 xiii. The Catocalinae are represented in the present 

 volume by sixty-three genera and 643 species, and 

 are characterised as follows : — Vein 5 of the hind 

 wing is developed fully and arises close to the 

 lower angle of the cell ; the eyes are smooth and 

 not overhung by "cilia " ; the mid tibiae are always 

 spined, and the fore and hind tibiae may also be 

 armed similarly. The subfamily is a modification 

 of the Quadrifid section of the Noctuidas ; it is 

 distributed fairly evenly in the temperate and 

 tropical zones, but has few arctic or alpine forms. 



Volcanoes : Their Structure and Significance. 



By T. G. Bonney. Third edition. Pp. 379. 



(London : John Murray, 1912.) Price 6s. net. 

 Prof. Bonney 's well-known volume was reviewed 

 at length in the issue of Nature for May 11, 

 1899 (vol. lx., p. 27). at the time of its first 

 publication. Many minor alterations have been 

 made in the present edition, and several para- 

 graphs inserted dealing with volcanic eruptions 

 which have take place recently. The chapter on 

 the theories of volcanoes has been considerably 

 modified so as to incorporate the results of 

 research accomplished during the last fourteen 

 years. Some new illustrations also have been 

 added. 



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 Radio-elements and the Periodic Law. 



At a meeting of the Royal Society on February 

 27th, Mr. F. Soddy made a verbal communication 

 which was published under the above title in the 

 Chemical News of the following day. The importance 

 of the conclusions which are drawn justifies an 

 examination of the evidence on which they rest. I 

 do not approach the question unsympathetically, and 

 I am quite willing to take some risks, but, when 

 asked to accept a theory, I like to draw a distinction 

 between a guess, a reasonable generalisation, and a 

 well-established conclusion. If Mr. Soddy only wishes 

 to put forward a theory which is not inconsistent with 

 the facts so far as they are known at present, I have 

 nothing to say, but if he claims anything approaching 

 to experimental proof, some critical comment may be 

 forgiven. 



Mr. Soddy believes in the existence of a number 

 of bodies which differ in molecular weight but "are 

 non-separable by any known process " ; these are also 

 supposed to have identical spectra. Among "known 

 processes" I count gravitation, diffusion, and mechan- 

 ical processes, such as separation by centrifugal forces, 

 among which diffusion, perhaps, is the only available 

 one. Is there any reason to suppose that molecules 

 which, ex hypothesi, differ in mass, cannot be 

 separated bv diffusion ? Some of the bodies concerned 

 are gaseous, others no doubt are volatisablc, and 

 though diffusion may not act very effectively, owing 

 to the close approximation of the densities, the pre- 

 sumption is that the molecules, having different 

 masses, travel with different speeds, and that it is 



