420 



NATURE 



[July 25, 1918 



K. Beer and Agnes Arber : The occurrence of multinu- 

 cleate cells in vegetative tissues. Binucleate or multi- 

 nucleate cells have been observed by the authors in 

 174 plant species belonging to fifty-nine families. 

 They have been found in each of the five classes of 

 living Pteridophyta, in Gymnosperms, and in Angio- 

 sperms. They occur in a wide range of tissues be- 

 longing to stern, root, and leaf. The multinucleate 

 condition has, in all cases, been found to arise by 

 mitotic division of the nucleus, and in no instance 

 have amitotic divisions been seen to play a part. — 

 Dr. J. H. Mummery : The epithelial sheath of Hertwig 

 in the teeth of man, with notes on the follicle and 

 Nasmyth's membrane. The author shows that the 

 "epithelial sheath of Hertwig" is present as a com- 

 plete organ in human teeth, and, as shown by von 

 Brunn in many mammalia, is the moulding or limit- 

 ing organ of the dentine of the root, being constantly 

 present where dentine is being deposited. ^ — H. H. 

 Jeffcott : The periods of lateral vibration of loaded 

 shafts. The rational derivation of Dunkerley's em- 

 pirical rule for determining whirling speeds. This 

 paper deals with the periods of lateral vibration of 

 loaded shafts, and gives the rational basis of Dun- 

 kerley's empirical method for determining the first 

 whirling speed of a shaft carrying a number of loads. 

 Results obtained bv the Dunkerley formula are com- 

 pared with the exact solutions in a few simple "cases. 

 The method employed is of general application, and 

 leads to a theorem connecting the several speeds of 

 vibration of a system of masses elastically connected 

 with the speeds of vibration of the partial systems 

 obtained by reducing to zero a given number of the 

 masses in turn in all possible combinations.— Prof. 

 Norman Collie and Dr. H. E. Watson ; The spectrum 

 of cadmium in the inactive gases. — C. F. Brush, Sir 

 Robert Hadfleld, and S. A. Main : Further experiments 

 on spontaneous generation of heat in recently hardened 

 steel. — ^T. Matsushita : The slow contraction of 

 hardened carbon st^^els. 



Dublin. 

 Royal Dublin Society, June 25.— Dr. G. H. Pethy- 

 bridge in the chair. — Dr. F. E. Hacliett : The twist 

 and magnetisation of a steel tube ifi a spiral magnetic 

 field. This paper deals with the verification of a 

 formula given by Knott in 1888 relating the Wiede- 

 mann effect to the Joule effect, viz. twist = length 

 (radius)-^ sin 20(61 + 62), where e, and e^ are the 

 longitudinal elongation and transverse contraction in 

 a given magnetic field. The theory was tested by 

 keeping the spiral field constant and varying the 

 pitch-angle o. Examination of the longitudinal 

 magnetisation under the same conditions shows 

 that the slight deviations observed from the 

 expected linear relation of the twist to sin 2a are 

 due mainly to the demagnetising effects at the ends. 

 — R. G. Allen : The absorption of water by vulcanised 

 fibre and erinoid on exposure to moist air, and the 

 consequent change of electrical resistance. Results 

 were given for thoroughly dried samples of vulcanised 

 fibre . and erinoid which were immersed in nearly 

 saturated air for measured intervals of time. The 

 quantity of water absorbed was found to be approxi- 

 mated related to the time of immersion by a simple 

 equation, and fibre was demonstrated to be much 

 more hygroscopic than erinoid. Other results were 

 given_ for these materials, showing the change of 

 electrical resistance with quantity of water absorbed 

 from moist air and the rapidity of decrease in resist- 

 ance, especially in the case of fibre, with increase of 

 this quantity. It was also shown that, whatever the 

 quantity of absorbed water in fibre and erinoid, the 

 same simple relation between temperature and resist- 

 NO. 2543, VOL. lOl] 



ance, common to many materials, including water, 

 was followed in every case. The latter result was 

 pointed out as giving strong support to the theory 

 that electricity is conducted through the material of 

 an insulator by the vehicle of water-films. 



BOOKS RECEIVED. 



Colour in Relation to Chemical Constitution. By 

 Dr. . E. R. Watson. (Monographs on Industrial 

 Chemistry.) Pp. xii+197. (London: Longmans, 

 Green, and Co.) 125. 6d. net. 



Wireless Telegraphy and Telephony: A Handbook 

 of Formulae, Data, and Information. By "Prof. W. H. 

 Eccles. Second edition, revised and enlarged. Pp. 

 xxiv+514. (London : Benn Bros., Ltd.) 



War Nursing : What Every Woman Should Know. 

 Red Cross lectures by Prof. C. Richet. Translated 

 by H. de Vere Beauclerk. Pp. xi+iig. (London: W. 

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Natural Science and the Classical System in Educa- 

 tion. Essays New and Old. Edited for the Com- 

 mittee on the Neglect of Science by Sir Ray Lankester. 

 Pp. ix + 268. (London : W. Heinemann.) 25. 6d. net. 



The Practice of Soft Cheesemaking : A Guide to 

 the Manufacture of Soft Cheese and the Preparation 

 of Cream for Market. Fourth revision by C. W. 

 Walker-Tisdale and T. R. Robinson. Pp. 106- 

 (London : J. North.) 3s. net. 



The War and the Coming Peace : The Moral Issue. 

 By Prof. M. Jastrow, jun. Pp. 144. (Philadelphia 

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A Short Handbook of Oil Analysis. By Dr. A. H. 

 Gill. Revised, eighth edition. Pp. 209. (Phila- 

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 net. 



CONTENTS. PAGE 



School and College Mathematics. By S. B. ... 401 



Lecithin and Allied Substances 402 



A Faunistic Survey 402 



Our Bookshelf 403 



Letters to the Editor:— 



Discovery of Neanderthal Man in Malta. (Illus- 

 trated.)— 'Proi. Arthur Keith, F.R.S. . . . 404 

 A Successful Method of Obtaining Amcebse for Class 



Purposes.— Dr. T. Goodey 405 



Scientific Plant Breeding . 405 



The Value of Insectivorous Birds. By Dr. Walter 



E. Collinge . 407 



Indian Industrial Progress 409 



Notes . . -410 



Our Astronomical Column : — 



Periodic Comets 414 



The Period of Sirius . . . . 414 



Two Spectroscopic Binaries of Long Period .... 414 



Stonyhurst College Observatory 414 



The Future of the Electrical Trades 414 



Italian Meteorology. By R. C, M 415 



Geology of the Barberton Gold-mining District 415 

 The Spinning-top in Harness. By Sir George 



Greenhill, F.R.S 416 



University and Educational Intelligence . 418 



Societies and Academies 419 



Books Received 420 



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