July 28, 1923] 



NA TURE 



14: 



tion of the important Buddhist sites beyond its north- 

 western frontier. It is satisfactory to learn that the 

 matter has now been amicably arranged. The French 

 Governmeht has also expressed readiness to welcome 

 the collaboration of British investigators, and the 

 existence of the concession will not affect their 

 participation. 



A LIST of the new books and new editions added to 

 Lewis's Medical and Scientific Circulating Library 

 during Jmae has just been issued by Messrs. H. K. 

 Lewis and Co., Ltd., 136 Gower Street, W.C. i. It 

 is sent free upon request. 



Messrs. J. and A. Churchill announce the early 

 publication of the translation of vol. 2, pt. 2 of 

 Molinari's " Organic Chemistry," completing this 

 section of the work. The new part will deal with 

 the esters, oils and fats, sugars and other carbo- 

 hydrates, cyclic compounds, dyestuffS; textile fibres, 

 proteins, etc. 



Upwards of 1600 works in botany, zoology and 

 general natural history, many of which are rare, are 

 included in the latest catalogue (New Series, No. 8) of 

 Messrs. Wheldon and Wesley, Ltd., 2 Arthur Street, 

 W.C.2. They originally belonged respectively to 

 Prof. G. A. Boulger, Mr. F. N. Campbell, Sir F. W. 

 Moore and Sir Edmund Giles Loder, Bart. The list 

 is worthy of perusal. 



Among the announcements of Messrs. Ernest Benn, 

 Ltd., are " The Art of the Chinese Potter," by A. L. 

 Hetherington and R. L. Hobson, which will illustrate 

 192 choice examples of pottery dating from the Han 

 Dynasty to the end of the Ming, in a series of coloured 

 and half-tone plates ; " The Art History of Ancient 

 Peru," by Drs. W. Lehmann and H. Doring, being 

 the first publication of the Research Department of 

 the Ethnographical Museum, Berlin, and " Intro- 

 duction to the Study of Chinese Painting," by A. 

 Waley, which will be compiled almost entirely from 

 native texts, few of which have been translated before. 



Our Astronomical Column. 



D 'Arrest's Comet. — No news of the detection 

 of this comet is yet to hand ; this is not altogether 

 surprising, as it has been noted faint at previous 

 returns ; and as it has not been seen for two revolu- 

 tions, the positions given may be somewhat in error. 

 The search is still possible in August ; in fact, the 

 maximum brightness is in the last week of August. 

 The following is a continuation of Mr. F. R. Cripps's 

 ephemeris (for midnight) : 



Decl. 



logr. 



o-i6o 



0-151 



0-143 



log A. 



9-837 

 9-837 



9-840 



V, A are the distances from sun and earth in astro- 

 nomical units. 



The comet should be looked for about 20° west of 

 south, as soon as the sky is dark. 



The Cepheid Variables and the Distance of 

 THE Clusters. — These variables were largely used 

 by Prof. Shapley in his deduction of the distances 

 of the globular clusters. In the last two years both 

 Prof. Curtis and the late Prof. Kaptevn have 

 challenged these distances ; they suggested values 

 about one-seventh of Shapley's. Kapteyn's result 

 was based on all the available proper motions of the 

 Cepheids ; he concluded that these were larger than 

 would be • expected on Shapley's formula of their 

 distance. Mr. R. E. Wilson, of Dudley Observatory, 

 Albany, returns to this question in Astron. Journ. 

 No. 821 ; he uses all Kapteyn's material, together 

 with a considerable amount of new matter, so that 

 his list contains eighty-four stars. He divides them, 

 as others have done, into the short-period cluster 

 type, and those with periods exceeding two days. 

 Mr. Wilson has also collected observations of radial 

 velocity for thirty of these stars, six being of type I. 

 Hi§ conclusion is that these short-period variables 

 are rapid movers in space, the indicated velocity 

 being of the order of 100 km. /sec. He therefore 

 considers that Kapteyn's distances for these stars, 

 which were based on a much lower assumption of 



linear speed, are too small. The stars of longer period 

 are presumably more massive, and their peculiar 

 speed is found to be 12 km. /sec. Wilson's estimate 

 of the cluster distances is of the same order as 

 Shapley's, but he suggests a reduction of the latter 

 by an amount not exceeding 40 per cent. 



Mr. Wilson also uses his results to test Kapteyn's 

 suggestion that Boss's proper motions in declination 

 need systematic correction by the formula -|-o-oi3' 

 cosine decl. The material is too scanty to give a 

 conclusion, but it suggests that a correction of half 

 the size indicated by Kapteyn is needed. 



Photography of Meteors. — The great difficulty 

 in " catching " a meteor on a photographic plate is 

 referred to by Dr. Harlow Shapley in a brief report 

 on a photographic survey for bright meteors (Harvard 

 College Observ. Bull., No. 788). Harvard College 

 possesses a series of plates extending over an interval 

 of twenty-three years. Each plate covers more than 

 twelve hundred square degrees, and the average 

 length of exposure is sixty-nine minutes. These 

 plates show stars to the eleventh photographic 

 magnitude or fainter, and were made with a one-inch 

 Cooke lens of thirteen inches focal length. The 

 most striking result of this systematic examination 

 of 641 direct photographs is the infrequency of 

 meteor trails. Four sets of regions and time intervals 

 were so chosen that each included the radiant point 

 and the date of a well-recognised meteor shown, 

 and the total exposure time for all these plates 

 amounted to 44,266 minutes. Thus, as is stated, 

 the present survey is equivalent to a photographic 

 search for bright meteors for 738 hours over a region 

 with a diameter of nearly forty degrees, and yet 

 only twelve meteors were recorded. The results 

 are briefly summarised as follows : 



-. J TO . Total Exposure 

 No. of Plates. min. 



Perseids . 

 Orionids . 

 Leonids 

 Andromedids 



95 



93 



143 



310 



6,379 



6,250 



9,528 



22,154 



Meteor 

 Trails. 



3 

 o 

 I 



NO. 2804, VOL. I 12] 



Erratum. — Meteor of July 11, p. no, last line. 

 For " 15° W. of south " read " 15° E. of south." 



