598 



NATURE 



[April 24, 1890 



•de conferences et professeurs, nous y consacrerons notre dtivoue- 

 ment, nos efforts : nous avons la confiance que, pour I'honneur 

 •de la Science et de la France, nous saurons fidelement le 

 remplir." 



SCIENTIFIC SERIALS. 



The American lournal of Science, April 1890. — On the 

 seolian sandstones of Fernando de Noronha, by John C. Bran- 

 ner. These sandstones lie upon the eastern or south-eastern 

 sides of the island, at an elevation of 70 feet on Ilha do Meio, 90 

 feet on Sao Jose, and about 100 feet on the Ilha Rapta, and at 

 the base of Atalaia Grande. The author has closely investigated 

 the formation, and finds that the material was originally de- 

 posited in the form of sand-dunes blown up by winds from 

 the south or south-east. Analyses of several specimens of the 

 rock are given. — A mountain study of the spectrum of aqueous 

 vapour, by Charles S. Cook. The author has devised a means 

 of producing an artificial line whose intensity can be varied at 

 will alongside the line whose intensity is required. The varia- 

 tions in the blackness of the artificial line are effected by the use 

 of a micrometer screw, the readings of which constitute an 

 arbitrary value of intensities. It is found, (l) that the spectro- 

 scope studies vapour height primarily, and humidity only 

 secondarily ; (2) during stormy weather vapour ascends to alti- 

 tudes greater than is usually supposed ; (3) the great absorption 

 of storm clouds is due to their great thickness, or to extensive 

 strata of damp air associated with them, more than to any 

 peculiar behaviour as clouds. — On the occurrence of basalt dykes 

 in the Upper Palseozoic series in Central Appalachian Virginia, 

 by Nelson H. Darton ; with nates on the petrography, by J. 

 S. Diller. — Additional notes on the tryolite from Utah, by W. 

 F. Hillebrand and E. S. Dana. The composition and crystal- 

 line form of this mineral are considered. — W. S. Bayley, on the 

 origin of the soda-granite and quartz-keratophyre of Pigeon 

 Point, Minnesota. These rocks have been previously described 

 by the author {Amer. yourn., January 1889). In the present 

 ■note the reasons are pointed out which lead to the conclusion 

 that the red rock is of contact origin, and produced by the action 

 of the gabbro upon the slate and quartzites. — Frank Waldo, in 

 recent contributions to dynamical meteorology, gives a general 

 idea of the nature of each of fourteen papers on meteorology ; 

 most of the papers being by German physicists. The attitude of 

 the writers towards meteorology is also indicated by reference to 

 other work done in the same direction. — Two methods for the 

 direct determination of chlorine in mixtures of alkaline chlorides 

 and iodides, by F. A. Goochand F. W. Mar. — ^On the occurrence 

 of polycrase, or of an allied species, in both North and South 

 Carolina, by W. E. Hidden and J. R. Mackintosh. The 

 analyses, so far as they go, show that a mineral previously 

 noticed (^w^r. yourn., November 1888) is very closely allied to, 

 if not identical with, the polycrase from Hitteroe, Norway, 

 analyzed by Rammelsberg. — Origin of some topographic features 

 of Central Texas, by Ralph S. Tarr.— On the formation of 

 silver silicate, by J. Dawson Hawkins. A simple method for 

 the preparation of this compound is described. The reaction 

 made use of is NaoSiOg + aAgNOj = AgjSiOg + 2NaN03. 



SOCIETIES AND ACADEMIES 

 London. 



Royal Society, April 17, — "Preliminary Note on Sup- 

 plementary Magnetic Surveys of Special Districts in the British 

 Isles." By A. W. Riicker, M.A., F.R.S., and T. E. Thorpe, 

 Ph.D., B.Sc, (Vict.), F.R.S. 



During the summer of 1889 we carried out additional mag- 

 netic surveys of the Western Isles and the West Coast of Scot- 

 land, and of a tract of country in Yorkshire and Lincolnshire. 



Both districts were selected with special objects in view. We 

 had found that powerful horizontal disturbing forces acted west- 

 wards from the Sound of Islay, from lona, and from Tiree, and 

 we had deduced a similar direction for the disturbing force at 

 Glenmorven from Mr. Welsh's survey of Scotland in 1857-58. 

 The whole district presents peculiar difficulties, partly from the 

 fact that local disturbance is likely to mask the effects of the 

 regional forces, partly because the normal values of the elements 



must be especially uncertain at stations on the edge of the area 

 of our survey. 



If, then, the general westward tendency of the horizontal 

 disturbing forces was due to some source of error, stations in the 

 extreme south of the Hebrides would in all probability be simi- 

 larly affected. If the directions of the forces were due to a 

 physical cause, such as a centre of attraction out at sea to the 

 west of Tiree, then the disturbing forces in the Southern 

 Hebrides would almost certainly be directed southwards 

 towards it. 



The observations made last summer prove (i) that the direc- 

 tion of the disturbing horizontal force at Bernera, which is the 

 southernmost island of the Hebridean group, is due south ; and 

 (2) that, as this point is approached from the north, the down- 

 ward vertical disturbing attraction on the north pole of the 

 needle regularly increases, which exactly agrees with the sup- 

 position that a centre of attraction is being approached. 



There is, therefore, now no doubt that there is a centre of 

 attraction on the north pole of the needle to the south of the 

 Hebrides and to the west of Tiree. 



(2) In one of the maps communicated to the Society last year 

 we drew two lines, bounding a district about 150 miles long 

 and 40 miles broad, in Yorkshire and Lincolnshire, and gave 

 reasons for the belief that a ridge line or locus of attraction lay 

 between them. 



This conclusion has now been tested by means of thirty-five 

 additional stations, with the following results : — 



(i) At all stations (with one exception) on or near the two 

 lines, the horizontal disturbing forces tend towards the centre 

 of the district they bound. 



(2) The downward vertical disturbing forces are greater in 

 the centre of the district than at its boundaries. In particular, 

 there are two well-marked regions of very high vertical force. 



(3) The greatest vertical force disturbances occur at Market 

 Weighton, where the older sedimentary rocks are known to 

 approach the surface, and at Harrogate, which is on the apex of 

 an anticlinal. 



(4) The central ridge line runs from the Wash parallel to the 

 line of the Wolds to Brigg. Thence it appears to turn west, 

 and reaches Market Weighton vid Butterwick and Howden. 

 One or two additional stations are, however, required to deter- 

 mine whether this bend is real, or whether the line runs direct 

 from Brigg to Market Weighton. From the latter town it 

 passes to the limestone district of Yorkshire and traverses its 

 centre. It has not yet been traced west of the line of the Mid- 

 land Railway between Settle and Hawes, but there is ground for 

 believing that it continues to the Lake District. 



Although, therefore, one or two points of detail remain for 

 further investigation, the* existence of a line of attraction 150 

 miles long is proved beyond the possibility of doubt, and for 

 about 90 miles its position is known to within 5 miles. 



There are, then, even in those parts of England where the 

 superficial strata are not magnetic, regions of high vertical force 

 comparable in size with small counties, and ridge lines or loci of 

 attraction as long and almost as clearly defined as the rivers. 

 Their course is closely connected with the geology of the 

 districts through which they run. 



Royal Meterological Society, April 16. — Mr. Baldwin 

 Latham, President, in the chair. — The following papers were 

 read : — The cold period at the beginning of March 1890, by Mr. 

 C. Harding. At the commencement of the month a rather 

 heavy fall of snow was experienced in many parts of England, 

 and very cold weather set in over the midland, eastern, and 

 southern districts, the temperature on the 3rd and 4th falling 

 to a lower point than at any time in the previous winter. The 

 lowest authentic thermometer readings, in approved screens, 

 were 5^ at Beddington, 6" at Kenley in Surrey and Hillington 

 in Norfolk, 7° at Chelmsford and Beckenham, 8° at Addiscombe, 

 9° at Reigate and Brockham, and 10° in many parts of Kent and 

 Surrey. At Greenwich Observatory the thermometer registered 

 13°, which has only once been equalled in March during the last 

 100 years, the same reading having occurred on March 14, 1845. 

 During the last half-century the temperature in March has only 

 previously fallen below 20° in three years, whilst during the 

 whole winter so low a temperature has only occurred in eight 

 years. — Note on the whirlwind which occurred at Fulford, near 

 York, March 8, 1890, by Mr. J. E. Clark. A sharp and heavy 

 thunderstorm occurred at York about 2.30 p.m. At the same time, 

 or shortly afterwards, a whirlwind passed a little to the south of 

 the city, from Bishopthorpe to Heslington, a distance of about 



