ZT' 



NATURE 



[January io, 191 8 



would render Dharmsala safe against any earthquake 

 that is likely to occur. 



The problem of mining thin coal-seams has recently 

 been the subject of considerable discussion in Great 

 Britain, and it is interesting to note that it has at the 

 same time been attracting attention in Canada, as is 

 shown by a recent publicatioti of the Canadian De- 

 partment of Mines, Bulletin No. 15, on the mining 

 of thin coal-seams as applied to the eastern coalfields 

 of Canada, written by Mr. J. F. Kellock Brown. The 

 author discusses the technical aspects of the question, 

 but lays most stress upon its economics. He points 

 out that the present coal industry of eastern Canada 

 is in a weak position, having reached its period of best 

 productivity, but beset with outside competition and 

 rising costs, and operated by over-capitalised con- 

 cerns, the earning capacity of which is only 3 or 4 per 

 cent, of their capital. He estimates that the coals 

 now being worked may well be exhausted in about a 

 century, and therefore proposes that the industry should 

 be reorganised, worked by powerful corporations or 

 combinations, and that legislation should compel the 

 working of a certain proportion of coal from the thin 

 seams along with that of the more easily wrought 

 thicker seams. He considers that "when properly 

 operated, and properly financed under reasonably 

 favourable conditions, 12-in. seams of coal can be 

 worked economically in eastern Canada to-day," 

 though it is doubtful whether many colliery engineers 

 in this country would fully concur in this conclusion. 

 In any event, the bulletin is an important contribution 

 . to the great problem of the proper and effective utilisa- 

 tion of the mineral resources of the British Empire, 

 and deserves careful study from this point of view, as 

 well as for the technical considerations involved. Under 

 the latter head numerous details of machine mining 

 and underground conveyer systems are given, together 

 with the actual operating costs in a few selected 

 examples. The author appears to have reached the 

 definite conclusion that in mining thin seams machine 

 work — not only machine mining, but "the application 

 of power to the whole operation of getting the coal, 

 from the commencement of the undercutting to the 

 placing of the coal into the mine cars " — is essential to 

 success. 



Part 3 of vol. vi. of the Science Reports of the 

 University of Sendai, Japan, contains the sixth, 

 seventh, eighth, and ninth reports of the Alloys Re- 

 search Institute of Japan, which all have reference to 

 the magnetic or other properties of iron and its alloys. 

 The eighth report, by Prof. Honda, deals with the 

 magnetisatlen of iron powders as the simplest form 

 of the problem presented by the magnetisation of 

 alloys. The powders used were of reduced iron mixed 

 with fine sand to obtain small amounts of iron per 

 c.c, and compressed to get densities approaching that 

 of solid iron. Rods of 0-5 cm. diameter 15 cm. long 

 were magnetised in a coil, providing fields up to 1000, 

 and the magnetisation measured ballisticallv. The 

 curve showing the relation between the specific mag- 

 netisation (the quotient of the intensity of magnetisa- 

 tion by the mass of iron per c.c. of the specimen) of 

 the solid iron is of the usual type, the bend or shoulder 

 occurring between fields 50 and 200, and the saturation 

 value of the specific magnetisation being 210. For a 

 powder containing three-fourths the iron per c.c. the 

 curve shows no shoulder, though it is convex upwards. 

 At a field of 1000 its specific magnetisation is only 

 140, and shows no sign of saturation. For smaller 

 quantities of iron per c.c. the curves become nearly 

 straight lines — that is, the specific magnetic suscepti- 

 bility becomes constant for each mixture, but decreases 

 as the mixture contains less iron. 



NO. 2515, VOL. 100] 



The latest list of Mr. F. Edwards, 83 High Street, 

 Marylebone, W.i (No. 380), contains 1066 items, and 

 is devoted to biography. It is not very strong in 

 science, but among the books offered for sale we 

 notice the memoir of " Sir Samuel Baker," by T. 

 Douglas Murray and A. Silva White; "Sir Joseph 

 Banks's Journal during Capt. Cook's First Voyage," 

 edited by Sir J. D. Hooker; "Life of Sir Joseph 

 Banks," by E. Smith ; the first edition of Washington 

 Irving's " Christopher Columbus : History of his Life 

 and Voyages " ; "Charles Darwin : Life and Letters," 

 edited by Sir F. Darwin; " Memoirs of the Life, Writ- 

 ings, and Discoveries of Sir Isaac Newton," by Sir 

 D. Brewster, and several lives of men of science which 

 have been published during the past few weeks. The 

 catalogue will be sent upon written application. 



Mr. W. Heinemann will shortly publish vol. ii. of 

 Dr. Montessori's "The Advanced Method." The work 

 will deal with the Montessori material, and the use of 

 it, for children up to the age of eleven years, and will 

 be illustrated. It is announced in connection with the 

 volume that an authorised Montessori Training Insti- 

 tute is to be established in this country, presided over 

 bv Dr. Montessori. 



OVR ASTRONOMICAL COLUMN. 



Encke's Comet. — Encke's comet, which has been 

 observed at every perihelion passage since 1819, has 

 once more been detected, the discoverer being Prof. 

 Schorr, at Bergedorf, Hamburg. The position on 

 December 30 at 5h. 27m. G.M.T. was R.A. 22h. 59m. 

 4-93S., N. declination 3° 17' 35". The comet was of 

 the 15th magnitude, but should brighten considerably 

 in the next few weeks. The observed R.A. was 

 smaller than the tabular by 4s., the declination smaller 

 by 40". These smair residuals indicate that Mr. Viljev's 

 calculated time of perihelion passage 1918 March 24-3 

 G.M.T. is not much in error, perhaps about o-2d. too 

 late. This adds certainty to Mr. Viljev's conclusion that 

 the object observed in September and November, 1916, 

 was not the comet. An ephemeris was given in 

 Nature of December 27. 



The Nearest Star Known. — In Circular No. 40 of 



the Union Observatory, Mr. Innes gives the results of 



observations made for the determination of the parallax 



of the interesting faint star near o Centauri to which 



he first directed attention about two years ago. The 



observations extended from May 26, 19 16, to August 



: 23, 1917, and were made with a micrometer attached 



to the 9-in. equatorial at Johannesburg. The resulting 



I value for the parallax is 0-88'', as compared with 



'■ 0-755" recently determined at the Cape Observatory 



by Mr. Votjte. The mean of the two values is 0-82". 



The largest parallax previously known is that of a 



Centauri, which Kapteyn gives as 0759", and it would 



thus appear that the Innes star is the nearest known 



star to the solar system. The proper motion of the 



i faint stai* is closely similar, in both magnitude and 



I direction, to that of a Centauri, notwithstanding the 



] separation of 2° 13'. Mr. Innes suggests Proxima 



I Centaurus as a convenient name for this small star. 



The visual and photographic magnitudes of the star 



; are 11 and 13 respectively. 



The Interior of a Star. — An interesting popular 



j account of his mathematical investigations relating to 



J the physical conditions in the interior of a star is given 



under this title by Prof. A. S. Eddington in Scieniia 



for January. Prof. Eddington considers that there is 



now overwhelming evidence in favour of the existence 



