May 5. 1 9 10] 



NATURE 



289 



lished in No. 201 of the Agricultural Sewi of the more 

 serious occurrences of pests during 1909. In only one dis- 

 trict, a comparatively small area in Barbados, was any 

 trouble experienced from the sugar-cane root-borer 

 (Diaprepes abbreviatus) ; the larger moth-borer {Castnia 



and proves to be 15 or 16 metres a year. The finest 

 material from the northern sandstones is probably re- 

 covered in the district of alluvial loams south of Kharga 

 oasis. 



Ix connection with Prof. Silvanus P. Thompson's recent 



ticus) was, however, reported from British Guiana. The experiments on the physiolc^ical effects of an alternating 



cotton-worm (Aleiia argillacea), which was very abundant magnetic field on the human body, Mr. A. A. C. 



during the season 1908-9, has given very little trouble Swinton, in a letter which appears in the Electrician 



during the present season, nor have any other cotton pests for April 22, directs attention to several simpler methods 



been reported. Scale insects continue to attack limes, but of producing the same effects which have been known and 



no severe outbreak has occurred during the year ; parasitic used bv medical men for some vears. If the current from 



fungi are known to occur on these insects, and probably 

 aid in keeping them in check. The scarabee, or Jacobs, 

 of the sweet potato (Cryptorhynchus batatae) has proved 

 serious in Barbados, and cannot yet be controlled ; new 

 methods of treatment are therefore being devised. Another 

 insect about which further information is required is a 

 small moth, the larva of which lives in the heads of ripen- 

 ing sorghum, and causes much damage. 



an ordinary magneto machine be passed from the hand to 

 a wet sponge held on the temple behind the eye, a faint 

 flicker will be seen, which increases in frequency as the 

 speed of the machine is increased. If the current is sent 

 through the head in other directions a metallic taste is 

 produced in the mouth. By making the arms and body 

 into the secondary of a coil of many turns carrying a high- 

 frequency current, a small incandescent lamp the terminals 



The sand-dunes of the Libyan Desert have been studied of which are in contact .with the two hands may be made to 

 by Mr. H. J. LI. Beadnell during a residence of three lij^'ht up. 



From a paper by Dr. L. .A. Bauer 

 in the March number of Terrestrial 

 Magnetism and Atmospheric Elec- 

 tricity, it appears that a more detailed 

 examination of the records of the 

 magnetic storm which accompanied 

 the eruption of Mont Pel6e on May 8, 

 1902, has led him to the conclusion 

 that the storm was not instantaneous 

 over the whole earth, but that it 

 originated about 14° west of Mont 

 Pelee and travelled eastward with a 

 velocity of about 7000 miles per 

 minute round the entire globe. This 

 result raised in Dr. Bauer's mind the 

 further question whether magnetic 

 storms in general are instantaneous 

 over the whole earth, and an examina- 

 tion of the records of the disturb- 

 ances of January 26, 1903, "and of the 

 seventeen cases tabulated by Mr. Ellis 

 in his Royal Society paper, has led 

 him to the further result that mag- 

 netic storms are not instantaneous over the whole earth, 

 but in general travel to the east, occasionally to the west, 

 with a speed of about 7000 miles per minute, which may- 

 be reduced considerably in the case of some of the larger 



A Belt of Dune<i in Kharga Oasis, looking sonth or downstream. From the Geographical Journal. 



years in Kharga oasis, some 300 miles south of Cairo 

 Geographical Journal, vol. xxxv., April, p. 379). Even 

 where superposed on irregular sands, the dunes show a 

 remarkable linear grouping from north to south. The 

 dunes of .Abu Moharik thus start west of Cairo, and thence and more complex disturbances, 

 form a belt 6 or 7 kilometres wide and 650 kilometres in 



length. The author traces the sand to the rocks of post- >!«• Arthur Morley contributes a useful article on the 

 Middle-Eocene age that border the Mediterranean, and not strength of materials under combined stresses in Engineer- 

 to the Nubian Sandstone of the southern region. Between *"g for April 29. Undoubtedly recent experiments on com- 



these two regions lies the tableland of Eocene limestone, 

 grains from which may supply more than 7 per cent, of 

 calcium carbonate to the dunes piled up in the oasis of 

 Kharga. The growth and movement of crescentic dunes 



bined stresses have furnished interesting information on 

 the behaviour of materials under static loads, but some 

 hasty applications of this information are very unfortunate. 

 .\ static determination of the tenacitv of a material is 



or barchans have been especially observed. By saturating I easily made, and may serve as a useful index of quality, 

 the concave side of a barchan with water, it became j but it is well known that a simple stress of about one- 

 possible to cut a section in it, showing a bedded structure 1 quarter to one-third of this amount will be sufficient to 

 formed by sand carried over from the windward side. Mr. ; cause fracture if frequently reversed in direction. What 

 Beadnell urges that this justifies the older view of the the conditions of failure may be under combined stresses 

 formation of the steep convex face, as against that of which fluctuate are, in the absence of experimental evidence, 

 excavation by scour suggested by Dr. Cornish. Dr. at present unknown ; but a safe load may as well be pro- 

 Cornish, however, in the discussion on the paper, attributes portional to the static tenacity as to the static shear stress 

 the stratification to sliding following upon scour. Steep as at elastic failure, and it is much too soon to speak of the 

 the inner face seems to the eye, Mr. Beadnell shows that entire revision of formulae and practice affected by accepted 



its slope cannot exceed 3^°. The average rate of pro- 

 gression of dunes in the Libyan Desert, from north to 

 south, is now for the first time measured over two years, 

 NO. 2 1 14, VOL. 83] 



theories, or to hope that controversy concerning the design 

 of crank-shafts is ended. Rather it would be correct to 

 say that only the fringe of the question has been touched. 



