094 



NATURE 



[July 28, 192 1 



regions are said to be under marked cyclonic control. 

 The northern States are more cloudy than the 

 southern, and the Pacific coast as a whole is less 

 cloudy than the Atlantic. July and August are the 

 least cloudy months, whilst in the southern States the 

 minimum cloudiness is in autumn. In Florida the 

 cloudiest season occurs during the summer months. 



The report of the National Physical Laboratory 

 for 1920 (the first year of the directorship of Sir 

 J. E. Petavel) records an unusually large number of 

 staff changes. Sir A. Schuster has become chairman 

 of the executive committee ; Mr. F. E. Smith has 

 left to become Director of Research at the Admiralty ; 

 and Messrs. C. C. Paterson, A. Campbell, A. Kinnes, 

 B. P. Dudding, E. A. Coad-Pryor, and Dr. N. Camp- 

 bell have resigned, and some of these posts have 

 not been filled. Mr. R. V. Southwell has been ap- 

 pointed superintendent of the aerodynamics depart- 

 ment. The fees for tests have been increased, and 

 the number of instruments sent for test has decreased 

 as compared with 1913, notably in the case of optical 

 and electrical instruments. A large amount of work 

 has been done for industrial research associations and 

 for Government Departments, but in future Admiralty 



work will be independent of the Laboratory. The 

 programme of work for the present year includes the 

 measurement of physical constants required in in- 

 dustry and in the medical profession, the improve- 

 ment of the tests for photographic lenses, the study 

 of the characteristics of three-electrode valves for 

 wireless telegraphy, the manufacture of length stan- 

 dards of high accuracy, investigations on lubrication, 

 tests of models of aeroplanes with air-screws running, 

 light alloys research, and investigation of the inter- 

 action of ships. 



The Bureau of Standards, Washington, has issued 

 a pamphlet on "The Spectrophotoelectrical Sensitivity 

 of Proustite," by W. W. Coblentz, which is now 

 ready for distribution, and may be obtained by anyone 

 interested by addressing his request to the Bureau. 

 This investigation is a continuation of previous work 

 on various substances. At 20° C. the spectrophoto- 

 electrical sensitivity curve of proustite has a wide 

 maximum in the ultra-violet, with a weak, ill-defined 

 band at o-6/t. By cooling with liquid air the intrinsic 

 sensitiveness is greatly increased, and there is a very 

 large development of this band, which now shows a 

 maximum at o-^ySfi. 



Our Astronomical Column. 



The August Meteors. — Mr. W. F. Denning writes : — 

 " This annual shower returns to a maximum on about 

 August II, and the circumstances are rather favour- 

 able this year, the moon being near her first quarter 

 and setting at iih. 19m. G.M.T. There is no reason 

 to expect an unusually abundant display, but it will 

 be sure to provide an interesting shower of bright, 

 streaking meteors. The larger objects should be 

 carefully recorded, so that their real paths may be 

 computed. The position of the radiant point and its 

 change of place ought to be determined on each night 

 when the atmosphere is clear enough for the purpose, 

 for the shower is already fairly rich at the end of 

 July, and is well maintained until the middle of 

 August. This date, however, does not limit its dura- 

 tion, for occasional meteors are seen towards the end 

 of the month. The morning hours are usually best, 

 for the radiant is at a greater altitude after midnight 

 than at an earlier period. Though this system of 

 meteors has been sedulously observed during a great 

 number of years, there is still much to be learnt con- 

 cerning its annual variations, date of maximum, 

 changes in the position and character of the radiant 

 point, and in the relative strength of the numerous 

 contemporary showers which are visible." 



Search for ^lETEORS from the Pons-Winnecke 

 Radiant. — Prof. Barnard reports that he watched for 

 meteors all night on June 24, 25, 26, and 27 ; although 

 the search was fruitless it has considerable negative 

 value as showing that the dense part of the meteor 

 swarm did not intersect the orbit of the earth, so that 

 it would appear probable that the shower of June, 

 1916, will remain the sole example of a shower^ from 

 the Pons-Winnecke radiant. 



Mr. R. G. Chandra, of Jessore, India, also reports 

 a fruitless search for meteors on the night of June 25. 

 He states that Prof. Ray, of Bolpore, saw two meteors 

 radiating from the neighbourhood of 6 Bootis. 



Prof. Barnard mentions a telephonic report of a 

 shower lasting ten minutes on the night of June 27. 

 No further particulars were available. 



NO. 2700, VOL. 107] 



Statistics of Proper Motions. — No. 30 of the 

 Publications of the Astronomical Laboratory at 

 Groningen, by Prof. J. C. Kapteyn and Dr. P. J. Van 

 Rhijn, is a continuation of the valuable studies in 

 stellar statistics that have appeared in this series. 

 It commences with a r^sum^ of recent catalogues and 

 other sources of our knowledge of proper motions, 

 such as Mr. Innes's researches with the blink micro- 

 scope. The question of the effective area of the sky 

 covered in each research is considered — that is, if a 

 catalogue is not exhaustive down to some assigned 

 magnitude, it is considered to be exhaustive for a 

 smaller area of the sky, determined by the number 

 of stars contained in the catalogue. 



One of the most interesting questions dealt with is 

 the number of stars in the whole sky with motion 

 between certain limits. The following table has been 

 formed from data in Tables 6 and 7 of the book. For 

 these large proper motions the distribution is shown to 

 be independent of galactic latitude. 



Limits of Prober Motion. 



No. of 



stars 



in whole 



sky, o'2" o'3" o'4" o's" o"6" o'y" o'8" 0*9 " I'oo' i'5o''2*oo'' 



Mag. 6 169 71 30 26 16 7 5 3 14 I 5 



7 304 120 56 61 40 23 12 6 13 3 3 



8 520 216 76 124 36 21 21 II 18 6 12 



9 1125 410 103 38 47 25 34 13 51 21 9 



10 1425 261 166 133 48 29 24 10 33 10 19 



11 1770 342 200 135 63 117 45 36 90 9 <y 



12 1770 450 450 68 45 23 23 90 113 45 o 



13 1620 690 400 225 135 23 113 45 23 23 28 



14 1490 800 350 158 68 113 45 o 000 



The 169 in the first line means that there are 169 

 stars in the whole sky with annual proper motion 

 between 0-2'' and 0-3" and magnitude between 60 and 

 69. Similarly in other cases. The figures for the 

 faint stars are rough, since thev are deduced from thr 

 examination of very limited areas. 





