Rotjnl Astronomical Society. 305 



" What' this fog is seems a question very difficult to solve. An 

 infinite numljcr of substances on the surface of the earth are con- 

 stantly giving out their peculiar vapours ; even metals do so, a fact 

 implied by their having a smell ; for to be perceived in that manner; 

 particles must be flying off from them as from camphor. How high 

 do such vapours ascend in the atmosphere, how long do they re- 

 main suspended, and are they at times precipitated, or are they de- 

 composed ? 



" Smoke appeai-s to play a part, though perhaps a very small one, 

 in the business. From the universal practice all over the colony of 

 ' burning the land,' or the bush, there is seldom a week passes with- 

 out there being numerous fires burning in one's neighbourhood. In 

 clear, calm weather the smoke from one of these has been seen rising 

 up, cumuliform, 3000 or 4000 feet in height, and then forming a 

 level stratum sometimes fifty miles in length, and this has continued 

 several days, the fire still burning and the calm still enduring. While 

 the dry fog jjrevails, a smoke from the plains has been seen to I'ise 

 up 4000 feet and be lost in the upper layers of this haze, while at 

 the same time smoke from the top of a neighbouring mountain 6000 

 feet high, has only risen up about 200 feet, and has then slanted off 

 downwards and mingled with the same. 

 ''** In clear weather, on Winterhock-berg the theodolite telescope 

 (aperture 2 inches, power 25) has shown a pile of rough stones (12 ' 

 feet high, 12 feet broad at the base, and 3 at the top) on the Cedar 

 mountains, nearly seventy miles distant, so clearly, that an object*' 

 one-third the breadth of the top would have been abundantly visible."^ 

 From the same station a man was seen on Picket Berg, 45 miles off;'' 

 and on this, one of Hottentot's Holland Sneew Kop, the spars at the^ 

 Lion's Rump signal station (40 miles off), have been most clearly 

 visible. And what is very deserving of notice is, that some of the'' 

 very best definition have been witnessed on these mountains in thal^ 

 middle of summer with a light northerly air; while at the same'' 

 time, in the level country below, a strong south-east wind has been 

 blowing with its usual accompaniment of large, faint, woolly blotches 

 in the place of what ought to have appeared, viz. stellar points." '^J 



Magnitudes of Stars. — " Bessel's recommendation of steel specula'! 

 reminds me of a series of astronomical jjhoenomena that are passing^' 

 unrecorded, viz. the changes in the magnitude of some stars. ' 



"In March 1843, Mr. Mackay wrote from Calcutta to Sir Johil'' 

 Herschel that ij Argus had become as bright as Canopus, from which 

 Sir John concluded that ij was making another step forward, and 

 would in time rival Sirius and the planets. But, after having for a • 

 few days in the beginning of the above-mentioned month approxi-' 

 mated to Canopus, ij dwindled down again very rapidly. But Sir Johtt'* 

 was not far out, for, although the star may not be advancing by suc-t'f 

 cessive steps, it seems to be doing the same by undulations ; for, in" 

 March 1843, it did not go down to the point whence it started, and'^ 

 it is now again on the increase. It is, and has been for a month, 

 brighter than Canopus, half-way indeed between him and Sirius, and 

 is very red. "^'^^ ''" '" '""•"'' -;iuju r-Myujiii'j JiujJ'i()i||iii 



Phil. Map, S. 3. Vol. 27. No. 1 80. October 1 84-5. X 



