2;o 



NATURE 



[April 21, 1910 



others have summaries in English. Scandinavian geology, 

 as is well recognised, has a special interest for workers 

 on our pre-Devonian rocks and for all interested in recent 

 modifications of our shore-lines. 



The first part has appeared of the comprehensive work 

 entitled " Handbuch der Regionalen Geologie," edited by 

 Profs. Steinmann and Wilckens, of Bonn (Heidelberg : 

 Carl Winter, 1910). This includes the whole of Denmark, 

 by Dr. N. V. Ussing, of Copenhagen, and is published at 

 the moderate price of 1.60 marks, or 1.20 marks to sub- 

 scribers. The scheme of the editors is already in full 

 operation, and some sixty contributors of various nationali- 

 ties are at work on the subdivisions of the eight royal 

 octavo volumes. Landscape illustrations are excluded, but 

 sketch-maps and sections are given in the text. The refer- 

 ences to original memoirs are likely to be especially useful. 

 The present part of 38 pages, so convenient to carry in 

 the hand-bag, will form a companion for all scientific 

 visitors to Denmark. One of the maps shows how the 

 post-Glacial uplift of Scandinavia has affected a large part 

 of the Danish peninsula and the islands. Bornholm falls 

 into the Scandinavian region, and contains rocks from the 

 pre-Cambrian up to the Liassic systems, unknown other- 

 wise in Denmark. Attention is directed to the Middle and 

 Upper Jurassic and Lower Cretaceous strata of Jutland, 

 represented only by boulders in the drift. The various 

 oscillatory movements that have given the kingdom its 

 present outlines are well stated on p. 26. 



A PRELIMINARY report on the mineral production of 

 Canada during the year 1909 has been prepared by Mr. 

 John McLeish, chief of the Division of Mineral Resources 

 and Statistics, and published by the Mines branch of the 

 Canada Department of Mines. The total value of the 

 mineral production during the year was upwards of 

 i8,ooo,oooZ., an increase of 5 per cent, over 1908. Of this 

 total, 49-9 per cent, represents metals, 49-7 per cent, non- 

 metallic products, the remaining 04 per cent, being mineral 

 products not reported. Coal is still the most important 

 Canadian mineral, and constitutes 27 per cent, of the total. 

 Silver occupies second place with 159 per cent., gold and 

 nickel come next with 108 and 10-5 per rent, respectively, 

 and copper contributes 7-8 per cent. The metals nearly 

 all showed an increased output compared with 1908, while 

 in the non-metallic class there is a larger number of pro- 

 ducts showing increases than those showing decreases. The 

 increases were very noticeable in the cases of corundum, 

 gypsum, natural gas, salt, and in the structural materials, 

 cement, clay products, lime, and stone. 



In a paper published in Petermann's Mitteilungen Dr. 

 Marquardsen, of Gottingen, reviews the present state of 

 our knowledge of the topography and hydrography of the 

 inland drainage area of the Sudan and Sahara. The total 

 area of this region is estimated at 2,139,000 square kilo- 

 metres. Dr. Marquardsen states some interesting results 

 with regard to Lake Chad ; the variations in size and 

 level do not, in his opinion, indicate a progressive change 

 in climate since its discovery by Denham in 1823 ; the lake 

 appears to be shifting northward and gradually filling up. 

 The question of the ultimate filling up of the whole basin, 

 and breaking through of the streams which now supply 

 Lake Chad, is discussed ; and in this connection special 

 significance is attached to the Logone-Tuburi bifurcation 

 and the activity of the source streams of the Benue. 



The climatology of 1909, as recorded at the Juvisy 



Observatory, is reviewed by MM. Flammarion and 



J. Loisel in No. 2 (1910) of the Bulletin de la Society 



■astronomiqtie de France. The form of the discussion and 



NO. 21 12, VOL. 83] 



of the comprehensive set of curves follows that of previous 

 years, each element in the climatological record being 

 discussed separately and compared with the same element 

 in former seasons and years. Thus we see that 1909 was 

 one of the coldest years since 1S85, the mean temperature 

 for the year (9-5° C.) being the lowest since 189 1 ; in the 

 matter of mean summer Qune, July, .-Xugust) temperature 

 the value (16° C.) was the lowest since 1886, when the 

 records were commenced. Similarly interesting compari- 

 sons are made for the other elements. 



Messrs. Geo. Philip and Son have sent us a card- 

 board model, designed by Mr. Rupert Hicks, to show the 

 relative positions of Halley's comet, the sun, and the 

 earth during the present apparition. The model consists 

 of a piece of stout cardboard 12 inches by 10 inches, near 

 the centre of which is fixed a gilded disc representing the 

 sun. Attached by an arm to the latter is a circle re- 

 presenting the earth, the revolution being provided for by 

 the sun being pivoted at the centre. Then on a longer 

 arm is affixed a model comet, which may describe an arc 

 representing that part of the comet's path lying within 

 the orbit of the earth. Thus one gets the comet's path, 

 relative to earth and sun, from March 10 to May 30, and, 

 by swinging the discs into their appropriate positions on 

 the dated arcs, it is possible to see at a glance the con- 

 ditions governing the visibility of the comet and its tail 

 on any specified date ; the tail is made long enough to 

 illustrate the probable passage of the earth through it on 

 May ig. The price of the model is is. net, post free 

 is. id., and as a method of illustrating to non-astro- 

 nomical people the various conditions under which the 

 comet appears and disappears the model should prove 

 instructive and interesting. 



The February number of the Journal of the Institution 

 of Electrical Engineers contains a communication made 

 to the Manchester section of the institution by Mr. J. W. 

 Warr on the electric ignition of internal-combustion 

 engines. Descriptions of the principal methods of electric 

 ignition at present in use are given, but the author e.x- 

 presses a decided preference for the high-tension method 

 both for stationary engines and for motor-cars. The 

 simplicity of the means of production of the current for 

 low-tension methods is more than compensated by the 

 -trouble introduced by the mechanical contact breakers 

 which are then necessary to produce the spark. Of the 

 various high-tension methods, Mr. Warr considers that 

 depending directly on a magneto machine to be the most 

 trustworthy. 



According to an article in the February number of 

 Le Radium, M. T. Bialobjeski has commenced at the 

 College de France an examination of the effects of the 

 and 7 rays of radium on the conductivity of solid 

 di(5^ectrics. His method is to use the dielectric in a con- 

 denser the plates of which are horizontal, the lower one 

 being connected through an electrometer to earth, while 

 the upper one consists of a thin sheet of aluminium foil 

 kept in contact with the dielectric by means of a ring of 

 lead. The rays from i milligram of radium bromide con- 

 tained in a platinum capsule closed by a mica window fall 

 on the upper plate of the condenser and pass through it 

 to the dielectric beneath. The potential difference between 

 the plates is maintained by storage cells, and can be in- 

 creased to 1800 volts. The current produced is measured 

 by the rate of motion of the electrometer needle. Sulphur, 

 paraffin, wax, and amber have up to the present been 

 examined. For discs more than i millimetre thick the 

 current was proportional to the electromotive force used. 



