January 8, 1920] 



NATURE 



477 



in Western Australia, South Australia, and Victoria, 

 but largely a failure in New South Wales and Queens- 

 land. 



The shortage of potassium salts and nitrates during 

 the war has directed attention to many possible sources 

 of supply previously neglected. In Memoir 14 of the 

 Geological Survey of South Africa Messrs. Frood and 

 Hall discuss the deposits of saltpetre found as an 

 interstitial filling along the bedding planes at the 

 base of the valleys in a region of hard ferruginous 

 shale near Prieska and Hay, Cape Province. No 

 satisfactory estimate is available of the average com- 

 position and depth of the deposits. Nitrification of 

 the animal excreta accumulating near the sheltered 

 portions of the cliffs is believed to be the source of 

 the nitrate, which then passed in solution along the 

 joint planes, producing irregular encrustations and 

 pockets. If this be the correct explanation of their 

 origin, it is improbable that the deposits could be of 

 any great depth. 



The Summary of Progress of the Geological Survev 

 of Great Britain for igi8 (issued in 1919) is of special 

 interest through its description of the bauxitic nature 

 of certain Carboniferous strata in Ayrshire. A clav of 

 Millstone Grit age has been found to be a good 

 refractory, with 26-50 per cent, of alumina, 2S-50 per 

 cent, of silica, and combined water 7-5-15 per cent. 

 Most of the alumina is combined with silica, probably 

 as kaolin, I»it there remains an excess, as in bauxitic 

 clays. This excess is, however, not easily soluble in 

 hydrochloric acid, unlike that in bauxite. Oolitic 

 varieties of the bed contain most free alumina. 

 Basaltic lavas underlie the clay, and the conditions 

 that produce laterite and bauxite seem to have pre- 

 vailed in southern Scotland in Upper Carboniferous 

 times. The discovery and value of this material will 

 stimulate observation in other localities of Car- 

 boniferous rocks. It is pointed out that the quality 

 of the material may vary considerably, and that the 

 presence of titanium dioxide, which occurs as rutile, 

 in a greater proportion than 5 per cent, reduces the 

 refractory property considerably. In the same Sum- 

 mary of Progress a record is given of the personal 

 and official services rendered by the staff of the Geo- 

 logical Survey during the five years of war. Among 

 others, our congratulations go out to Capts. E. B. 

 Bailey and J. E. Richcy. 



In a valuable paper read before the Royal Society 

 of Edinburgh (Proceedings, vol. xxxix., 1919, pp. 157I 

 208), Prof. C. G. Knott continues his investigations 

 on the propagation of earthquake-waves through the 

 body of the earth. In his new analysis Prof. Knott 

 does not assume any relation between the velocity of 

 propagation and the distance from the earth's centre. 

 His work, which must have been most laborious, leads 

 him to the following conclusions. He finds that the 

 seismic rays of both the condensational and the distor- 

 tional waves are concave outwards until they reach a 

 depth of about three-tenths of the earth's radius. To 

 this depth, then, the velocity of propagation must 

 increase with the depth. It then becomes nearly con- 

 stant, but at still greater depths it decreases a little, 

 so that the rays there are slightly convex outwards. 

 NO. 2619, VOL. 104] 



The data furnished by seismological observatories en- 

 able him to trace the rays to a depth of six-tenths of 

 the earth's radius, but not beyond. At or near this 

 depth the distortional wave seems to die out, for at 

 arcual distances of more than 120° from the epicentre 

 their characteristic appearance in our seismograms is 

 lost. Dr. Knott thus arrives at a conception of the 

 earth's interior which is practically the same as that 

 advanced by Mr. Oldham thirteen years earlier : that 

 the earth consists of an elastic solid shell down to a 

 depth of about half the earth's radius, that here the 

 rigidity breaks down, and that at a depth of about 

 six-tenths of the earth's radius the elastic solid shell 

 gives place to a non-rigid nucleus of measurable com- 

 pressibility. 



.Soi'THPORT, by its report of the meteorological 

 observations made at the Fernley Observatorv during 

 the year 1918 and discussed by Mr. Joseph Baxendell, 

 the meteorologist to the Borough Corporation, adds 

 much to our knowledge of the weather at one of the 

 principal P^nglish health resorts. The report contains 

 more than detailed observations of the weather, and 

 now that the observatory has continued for forty-seven 

 years the results yield values of much importance. Two 

 local atmospheric pollution stations were started during 

 the year, one to be representative of urban and the 

 other of rural Southport. Hourly wind-direction- 

 frequenc\' normals are given numerically, as well as 

 in diagram form as a frontispiece; they show a pre- 

 ponderance of southerly winds in the winter and of 

 westerly and north-westerly winds from off the sea 

 during the day-hours in the summer months. Mr. 

 Baxendell hopes definitely to establish a marked and 

 persistent meteorological periodicity of nearly 51 years, 

 which, he states, is especially noticeable in wind direc- 

 tion. The year 1918 was marked by general warmth 

 and wetness, resulting from a very abnormal pre- 

 dominance of winds from the warmer and more humid 

 half of the compass (south-east through south to west). 

 The table giving the rainfall with different wind direc- 

 tions shows that 78 per cent, of the total amount of 

 rain was with winds from these directions. 



The Fifth and Sixth Reports of the Director of 

 Veterinarv Research of the Union of South Africa 

 contain an account by Mr. H. H. Green of an im- 

 proved method for the estimation of small quantities 

 of arsenic by micro-titration with iodine. It was 

 used for determining the fate of ingested and injected 

 arsenic in sheep. Bacteria capable of oxidising sodium 

 arsenite and reducing sodium arsenate have been 

 isolated from arsenical cattle-dipping tanks. Examina- 

 tion of maize-milling products by dietetic experiments 

 upon pigeons shows a close parallelism between the 

 distribution of vitaminc and phosphorus in individual 

 maize-kernels, but not in different samples of maize. 

 In the absence of information about the original grain 

 and the extent of milling, microscopic examination 

 would provide a safer test than the estimation of 

 phosphoric acid. An extensive study of diets con- 

 taining varying amounts of vitamine shows that the 

 daily demand of pigeons for vitamine is not constant, 

 but depends upon the extent of exogenous meta- 

 bolism. 



