S.A. CLIMATE AND AVIATION. 127 



rain-storms or line-sqiialls at very short notice. But the avia- 

 tor has also to be on his guard when the weather is ideally per- 

 fect, when a cloudless sky and gentle zephyrs prevail. On such 

 days the heating of the soil by the sun's rays gives rise to in- 

 numerable atmospheric whirls, which sometimes become visible 

 as dust-devi'ls ; the diameter and length of these whirls vary 

 greatly, but it is seldom that one is less than 20 to 30 feet 'n 

 diameter. An encounter with these whirls would probably mean 

 an upsetting of the unfortunate aeroplane. 



It is noticeable that the show-flights made by aviators who 

 visit South Africa have all taken place at the time of sunset ; at 

 this time of the day the atmosphere is relatively quiescent, Avhirls 

 and sudden gusts of wind being unusual. Still, better conditions 

 prevail at sunrise, but it would be impossible to get an audience 

 at that time. 



A book to be called " Charts of the Atmosphere for Aero- 

 nauts and Aviators " is being issued by the authorities of the Blue 

 Hil'l Aleteorological Observatory, near Boston, U.S.A., and will 

 be published by John Wiley and Son, oi New York. This book, 

 it is announced, will deal fully with the bearings of meteorology 

 on aviation. 



The successes already achieved by aeroplanists in the Northern 

 Hemisphere are sufificient to show that the investigation of the 

 non-surface movements of the atmosphere over South Africa 

 call for investigation by means of kites and baUoons, following 

 the lines of similar work in the Northern Hemisphere. 



Thej 191 1 Comets.— Several photographs of Kiess's 

 comet, i()i]/^ were taken at the Transvaal Observatory during 

 Augu;>t, and it is intended to publish the whole series in one of 

 the Observatory Circulars. The comet was visible to the naked 

 eye for about a week, but was never brighter than the fifth 

 magnitude. With respect to the more recently discovered comets 

 it is noted that, during October, Brooks' comet, igiic, had been 

 increasing in brightness, and on the 21st, with the R.A. of I2h. 

 40m., and a N.D. of 15 deg. 13 min., it had attained a magnitude 

 of 2.8, and had been visible in the morning for over a week. 

 Ouenisset's comet. 191 1/. and Beljawsky's comet, 1911(7, had 

 both decreased in brightness, the former being of 6.8 magnitude 

 and die latter 3.4 on October 20th. The position of Quenisset's 

 comet was on that date I5h. 40m. R.A., and 26 deg. 47 min. N.D., 

 while that of Beljawsky's comet was I4h. 53m. R.A., and i deg. 

 52 min. S.D. According to Prof. Nijland's observations at 

 Utreclit, tlie tail of Beljawsky's comet was 15 deg. long on 

 October ist, and of a broad parabolic type. 



