338 



NATURE 



[January 19, 191 1 



this and other cases, based on the suggestion of Daly 

 that igneous magmas are essentially basic at the outset. 

 In a paper on " The Classification of the Post-Carbon- 

 iferous Intrusive Igneous Rocks of the West of Scotland " 

 (Transactions of the Geol. Soc. of Glasgow, vol. xiii., 

 p. 298), Mr. Tyrrell gives a useful account of the dis- 

 tribution of the various types. In cooperation with Mr. 

 N. Martin, he describes the geology of the Auchineden 

 district io the Kilpatrick Hills (ibid., p. 322), and con- 

 tinues (p. 337) with an account of the igneous rocks of 

 the vents and lava-flows. These prove to be olivine- 

 basalts, though the sills were previously thought to be 

 trachytic, on account of their fluidal structure and pale 

 crusts. They belong to the late Palaeozoic series. In a 

 notice of rocks near Ballantrae (ibid., p. 283), Mr. Tyrrell 

 points to a granulitic diorite as a dolerite or gabbro meta- 

 morphosed by a later intrusion of serpentine. There is a 

 pleasing sense of original outlook in these papers. 



The Geological Survey of Ireland has issued a memoir 

 by Messrs. Kilroe, Hallissy, and Seymour on the soils of 

 the agricultural station at Ballyhaise (price is. 6d.), 

 accompanied by a map showing types of soil and the 

 underlying rocks, on the scale of eight inches to one mile. 

 The methods adopted by this Survey for the examination 

 of soils are fully stated. .Another memoir, by Messrs. 

 G. A. J. Cole and T. Crook (price is. 6d.), describes the 

 submarine geology of the west coast of Ireland, so far as 

 it can be known from the numerous rock-specimens 

 dredged up by the official Fishery Survey. The amount 

 of mingling of material by glacial drift-action appears to 

 be very small on the west coast. .Areas of Upper Creta- 

 ceous and Cainozoic limestone are indicated off the Kerry 

 coast. .As in the Ballyhaise memoir, a coloured map is 

 included in the publication. 



Prof. Cole describes (Proc. R. Irish Acad., vol. xxviii., 

 sect. B, 19 10, p. 113, price 6d.) the phenomena of weather- 

 ing on the surface of a sheet of fine-grained diorite near 

 Rathmullan, in Donegal, which is known as the " picture 

 rock " or " scribed rock." The residual spheroids lie in 

 box-like enclosures, the walls of which result from the 

 toughening of the rock by the development of amphibole 

 inward from its joint-planes. 



In the Irish Naturalist for September, 1910, the Rosa- 

 penna area in northern Donegal is systematically de- 

 scribed. Among the papers on its natural history is an 

 excellent one on the geological structure, bv Mr. J. de W. 

 Hinch. ' G. A. J. C. 



RUSSIAN MAGNETIC OBSERVATIONS. 



TJNDER the title "Die Variationen des Erdmagnet- 

 ^^ ismus " Prof. Ernst Leyst has written a paper, 

 occupying 250 pages and four plates, in the BtiUetin de la 

 Societe Imperiale des Naturalistes de Moscou for 1909. 

 It deals with magnetic data from the Russian observa- 

 tories at Pavlovsk (St. Petersburg), Irkutsk, and 

 Katharinenburg, and with some corresponding data from 

 Potsdam and Greenwich. The paper contains valuable 

 statistical data for Pavlovsk, such as the secular changes 

 of all the magnetic elements from 1873 to 1906, and diurnal 

 inequalities derived from a 33-year period. Its main 

 object, however, is to investigate the relations borne to 

 terrestrial magnetism by sun-spot frequency and barometric 

 pressure. .A number of the data bearing on the sun-spot 

 connection should be useful, such as diurnal inequalities in 

 years of sun-spot maximum and minimum at the several 

 stations. But their utility would have been greater if the 

 numerical relationships between magnetic and solar pheno- 

 mena had been gone into more critically. . .A good deal 

 has been already done on these lines, even for some of 

 (he stations considered by Dr. Leyst, of which he seems 

 unaware. 



The parts of the memoir having a chief claim to novelty 

 relate to the influence of sun-spot frequency on secular 

 change and on the annual inequality, and to the relation 

 between barometric pressure and the diurnal variations. 

 Dr. Leyst finds secular change of declination to be more 

 rapid near sun-spot maximum than near sun-spot mini- 

 mum at all the stations included in his research except 

 Katharinenburg. For the ratio borne by the rate of 

 secular change at sun-spot maximum to that at sun-spot 



NO. 2 15 I, VOL. 85] 



minimum he finds nearly 2 : i at Greenwich and more than 

 3 : I at Irkutsk. In the case of the annual inequality 

 i.e. the variation shown in the mean monthly values ah. 

 elimination of the secular change — he concludes in pp. 

 206-7 that the range is increased at sun-spot maximum for 

 declination and inclination, but diminished for total force. ' 

 As regards barometric pressure, Dr. Leyst finds the range > 

 of the magnetic daily oscillations, both regular and 

 irregular, at Pavlovsk to be larger on days of high, 

 barometric pressure than on those of lowest pressure, tli 

 phenomenon being specially conspicuous near sun-sp 

 maximum. 



The author's zeal, as evidenced by the great amount oi 

 labour expended in his investigations, merits warm appre- 

 ciation. One's confidence, however, in his conclusions 

 would have been greater if the work had shown moi 

 distinct evidence of critical insight. 



Lines of no secular change seem to traverse continen 

 with continuous velocity. Their passage must occur at son 

 stations in sun-spot maximum, and at others in sun-si>*)L 

 minimum, and must mark in either case a time when secular 

 change numerically considered is a minimum. In short, 

 secular change, while seldom varying rapidly with the geo- 

 graphical coordinates, is essentially a local phenomenon, 

 whereas sun-spot frequency is not. The secular change re-, 

 suits assigned by Dr. Leyst to Greenwich are certainly not. 

 fairly representative of sun-spot maximum and minimum 

 there. They show not the least resemblance to some which 

 the present writer has deduced for Kew from the longer 

 period 1860-1909. If a difference of the kind supposed by 

 Dr. Leyst does exist, it is in England, at least, of a com-, 

 paratively trifling character. As to the annual inequality, 

 that of declination — the element which ought to possess ' 

 least uncertainty" — presents the suspicious features that the 

 ranges obtained have usually diminished as the number 

 of years included was lengthened, while the types obtained 

 at comparatively near stations have differed. In Dr. 

 Leyst 's case the results are derived from only two or three 

 groups of three-year periods at either sun-spot maximum 

 or sun-spot minimum, so that more than usual uncertainty 

 attaches to the elimination of the secular change. Of all 

 Dr. Leyst 's conclusions, that as to the relations between 

 the diurnal variations and the barometric pressure is un- 

 doubtedly the most remarkable. The figures which I 

 gives for declination and horizontal force show durii , 

 summer, not a small, but a large difference between the 

 ranges of the diurnal inequality and the absolute ranges 

 (absolute maximum less absolute minimum) on days of 

 highest and on days of lowest barometer at Pavlovsk. In 

 winter the phenomenon is much less apparent, which leads 

 the author to regard the case as one of association and 

 not of direct cause and effect. 



If confirmed, the result, it need hardly be said, would 

 be of great theoretical importance. A matured opinion on 

 the question could be attained only by a minute study of 

 observational data. Thus an independent investigation of 

 data from some second observatory by a -competent critic 

 is to be desired. Several theoretical considerations natur- 

 ally present themselves. Large absolute magnetic ranges 

 are intimately associated with highly disturbed conditions, 

 and such conditions are normally, at least, not local. High 

 or low barometric pressure, on the other hand, is an 

 essentially local phenomenon. A high at St. Petersburg 

 means a low somewhere else, often even within the con- 

 fines of Europe. If there is any such general association 

 as Dr. Leyst supposes, a high barometer at Pavlovsk must 

 be a symptom of a special set of conditions affecting an 

 area much larger than that the barometric pressure of 

 which is above the average. C. Chree. 



THE MICHAEL SARS NORTH ATL.ANTIC 

 DEEP-SEA EXPEDITION, 1910.^ 

 TN August, 1910, Sir John Murray offered to defray | 

 ■'■ the expenses of an expedition to the North .Atlantic ; 

 with the Norwegian research steamer Michael Sars. Th 

 Norwegian Government, too, showed itself very indulg. 

 towards the enterprise, and placed the vessel entirely 

 our disposition ; and my colleagues, who have so 1< ' 

 1 From a paper read before t!ie Royal Geographical Society on Januar\ 

 by Dr. Johan Hjort. 



