loS 



NA TURE 



[March 2}, 1910 



abbreviated, and its price in paper covers is 6d., or in 

 cloth, with Dr. Bastian's portrait as frontispiece, is. net. 



A CATALOGUE of rare and valuable books and autograph 

 documents and letters has been issued by Mr. Bernard, 

 Quaritch, of Grafton Street, London, \V. The catalogue 

 runs to 336 pages, and contains full sections dealing with 

 works on astronomy, mathematics and physics, topography, 

 and other subjects likely to appeal to scientific readers. 



A SEVENTH edition of "A Treatise on Ore and Stone 

 Mining," by Sir Clement Le Neve Foster, F.R.S., has 

 been published by Messrs. Charles Griffin and Co., Ltd. 

 The work appeared first in 1894, when it was reviewed 

 at length in Nature (vol. 1., p. 543) by the late Mr. Bennett 

 H. Brough, who was afterwards responsible for the sixth 

 edition, issued in 1905, and reviewed in Nature of 

 January 4, 1906 (vol. Ixxiii., p. 220). The present issue 

 has been revised by Prof. S. Herbert Cox, who has adhered 

 to the original general scheme of the book. The price of 

 the treatise is 28s. net. 



The issue of the British Journal of Photography for 

 March 18 is the third of the special " colonial " numbers, 

 in which that journal addresses itself specially to photo- 

 graphers and photographic dealers abroad. The enlarged 

 text pages contain contributions on studio matters, in- 

 cluding the first of a series of articles for the young pro- 

 fessional portraitist on securing different effects of light- 

 ing. Mr. Edgar Clifton writes on the care of lenses in 

 the tropics, Mr. Welborne Piper on the adjustments of 

 the enlarging lantern, whilst a large proportion of the 

 letterpress deals with recent introductions by photographic 

 manufacturers. 



OUR ASTRONOMICAL COLUMN. 



The Solar Eclipse of 1912 April 17. — In an article 

 published in the Revue generale des Sciences for 

 February 15, M. D. Savitch discusses at full length the 

 circumstances of the solar eclipse of 19 12 April 17. 



The central line passes through Portugal, the Bay of 

 Biscay, and across France to Belgium, its direction being 

 north-east. It passes within ten miles of Paris. Only 

 about three times a century is an eclipse total in France. 



The magnitude of the eclipse along its central line is 

 continually diminishing, and the character of the eclipse 

 changes from total to annular. The point, however, where 

 this change takes place can hardly be assigned with 

 certainty, for it is largely displaced by a small change in 

 the adopted semi-diameter of the moon ; the difference of 

 I •18" between the values used by the Nautical Almanac 

 and the Connaissance des Temps is sufficient to displace 

 it by some hundred miles from a position out at sea to 

 the neighbourhood of Paris. 



In any case, totality is too short for the eclipse to be 

 of much value in the usual way. Nor is there much reason 

 to expect better results than usual from observations to 

 determine the moon's position. No eclipse since 1715 plays 

 a prominent part in determining the position of the moon, 

 and the eclipse of 1715 and its predecessors are important 

 because they are ancient rather than because they were 

 accurately observed in the modern sense of the word 

 accurate. 



M. Savitch 's article is clear, and illustrated by an 

 excellent map. 



The Comets (1910a and Halley's). — A large number of 

 observations of comet 1910a are published in No. 4392 of 

 the Astronomische Nachrichten, including those made at 

 Kodaikanal, Cambridge, Helwan, and Greenwich. Mr. 

 Michie Smith reports a number of positions, several of 

 which, it is interesting to note, are referred to positions 

 of a sun-spot. On January 31 Mr. Evershed traced the 

 tail to a distance of 27° from the head. 



Herr Konkoly reports the presence of the three hydro- 

 carbon bands, in the spectrum of the comet, on January 26, 

 and states that the continuous spectrum was faint, whilst 

 a fourth band was suspected. 



NO. 2108, VOL. 83] 



Dr. Kobold has carried his ephemeris back to the 

 beginning of November, and shows that, although the 

 comet was probably brighter than the sixth magnitude as 

 early as December i, it was apparently so near the sun 

 as to render its discovery improbable. The ephemeris 

 published in No. 4393 of the Astronomische Nachrichten 

 indicates that the comet may become observable again 

 about the first week in April as a morning star, but it 

 will be faint and difficult. A note in the Observatory for 

 March emphasises the necessity for such observations being 

 made, if possible, because of their value in determining 

 more rigidly the exact form of the orbit. 



Dr. F. J. Allen kindly sends us a beautiful drawing of 

 the comet depicting its form as he saw it on January 30 

 from the Mendip Hills ; the observations were recorded in 

 our article of February 10 (Nature, No. 2102, p. 441). 

 He directs especial attention to the pronounced curve of 

 the tail towards its extremity, the direction beyond 

 a Pegasi, the uppermost star shown, being nearly hori- 

 zontal, and states that the comet as here shown is, 

 relatively to the stars, too bright, while the head is perhaps 



Comet igioa. From a drawing by Dr. F. J. Allen. 



a little too large ; but the form and extent of the tail are 

 as he saw it. 



Dr. Allen, referring to the passage of the earth through 

 the tail of Halley's comet on May 18, suggests that a 

 well organised attempt should be made to collect some of 

 the cometary dust which may then enter our atmosphere. 

 It will be remembered that Prof. Turner, in his recent 

 Royal Institution lecture, suggested that some such attempt 

 should be made, by " bottling " some large quantities of 

 the atmosphere. It is obvious that to have any hope of 

 success the " bottling " would have to be done on a very 

 large scale and under the most favourable and rigid con- 

 ditions. Dr. Allen suggests a large chamber, carefully 

 prepared and situated in a position where the air is usually 

 very free from contamination, through which immense 

 quantities of the atmosphere could be drawn and filtered. 

 The filtering should be carried on before, during, and after 

 May 18, in order that differential tests might be applied to 

 determine the extra-terrestrial origin of the collected dust. 

 As the cometary dust, and gas, may take days, or weeks, 

 to diffuse sufficiently to reach the earth's surface, the ex- 

 periment should be continued for some time after the 

 critical date, thus affording opportunity to detect any 

 differences in the collected matter. 



