654 



NATURE 



[August 21, 19 13 



which the author erects two new genera — Disichthvs 

 and Peleichthys — and three new species — Acrolepis 

 addamisi, Disichthys kimberleyensis, and Peleichthvs 

 kimberleyensis. The fossils occur on slabs of sand- 

 stone which were taken from the Wesselton and De 

 Beers Mines, and from the absence of conspicuous 

 sandstones in the Ecca beds of the vicinity, and the 

 occurrence in another slab of Chelyoposaurus williamsi, 

 they are in all probability of Beaufort age. Denuda- 

 tion has removed all trace of the parent rocks from 

 the locality. — W. A. D. Rudge : The daily range of 

 atmospheric potential gradient at Bloemfontein and 

 the influence of dust storms. An account is given of 

 observations at Bloemfont.in between July and Decem- 

 ber, 1912, with a Bendorff recording electrometer. 

 The values of the potential gradient at hourly intervals 

 are given for the whole period, and curves showing 

 the daily range of the potential gradient are given for 

 selected cases. These curves show (i) the normal 

 range on clear calm days ; (2) that on days when some 

 dust was observed ; (3) that on verv dusty days ; and 

 (4) some special cases. The normal curves are similar 

 to those taken in other parts of the world, but those, 

 for dusty days show great differences. In class (2) 

 the dust is present in quantity sufficient to keep the 

 potential almost at zero whilst in (3) for a considerable 

 part of the day there is a very strong negative poten- 

 tial gradient amounting to thousands of volts per 

 metre. This negative result is caused by the clouds 

 of fine siliceous dust raised by the wind, "as has been 

 shown by the author in previous communications. A 

 negative potential gradient was never recorded unless 

 dust was blowing or rain falling. Wind alone had 

 practically no influence. The rain which fell during 

 the period under observation was invariablv negatively 

 charged. — J. C. Beaftie : Further magnetic observa- 

 tions in South Africa. Results of observations in 

 various parts of South Africa during 1910-13. The 

 greater number of the observations was carried out in 

 the western Transvaal, British Bechuanaland, and 

 Bushmanland, In addition a number of repeat 

 stations were re-occupied. — J. C. Beattie : Magnetic 

 maps of the western and northern parts of the Union 

 of South Africa and of Great Namaqualand for the 

 epoch July 1, iqoS. Maps are given showing; the true 

 isogonics. the true isoclinals, and the true lines of 

 equal horizontal intensitv for the above region. — T. 

 Muir : Note on Clebsch's theorem. 



BOOKS RECEIVED. 



The Microtomist's Vade-Mecum. By A. B. Lees. 

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Le Froid industriel. By Prof. L. Marchis. Pp. 

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A Plea for the Younger Generation. By Cosmo 

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Coast Erosion and Protection. By E. R. Matthews. 

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A New School Geometry. By R. Deakin. Part ii. 

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General Chemistrv Laboratory Manual. By Prof. 

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The English Convict : a Statistical Study. By Dr. 

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CONTENTS. page 



Ethnography of Northern Nigeria 629 



Physiological Pathology. By Prof. H. R. Dean . . 630 



Vegetable Alkaloids. By C. Simmonds 630 



Recent Books on Physics 631 



Our Bookshelf 632 



Letters to the Editor: — 



The Host-Embryonic Development of the Spiny 



Lobster. {Illustrated. ) — Prof. E. L. Bouvier . . 633 



The Origin of Actinium. — Frederick Soddy, F.R.S. 634 

 Radium anil the Evolution of the Earth's Crust. — 



R. D. Oldham, F.R.S '. 635 



Poroscopy : the Scrutiny of Sweat-pores for Indentifi- 



cation. — Henry Faulds .... 635 



Calanus-a Further Record. — Prof. W. A. Herd- 

 man, F.R.S 636 



The Structure of X-Radiation.— W. F. D. 



Chambers ; I. G. Rankin 636 



Scientific Mountaineering in India. (Illustrated.) . 637 

 A Criticism of Modern Methods of Medical Edu- 

 cation 639 



Liquid Crystals and the X-Ray Work. Dr. A. E. H. 



Tutton, F.R S 640 



The Piltdown Skull 640 



Helminths and Cancer 641 



Notes 641 



Our Astronomical Column : — 



A Star with Large Proper Motion 645 



" Giant " and " Dwarf" Stars 645 



The Stationary Radiation of Meteors 645 



The Lancashire Sea Fisheries Laboratory 646 



British Forestry .... 646 



The Manufacture of Artificial Teeth. By R. D. 



Pedley . . 647 



The Mutations of Oenothera. By Dr. R. Ruggles 



Gates . . . 647 



Observations in the South Magnetic Pole Area. 

 (With Map.) By Prof. T. W. Edgeworth David, 



F.R.S ' 64S 



Meroe : Four Years' Excavations of the Ancient 



Ethiopian Capital. By Piof. John Garstang . . . 651 



University and Educational Intelligence 652 



Societies and Academies 653 



Books Received 654 



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