Scientific Intelligence. — Meteorology. 177 



This appearance was neither preceded nor followed by any 

 lightning or explosion ; the column was vertical and motionless, 

 no rotary motion being observed. — Bib. Univ. June 1830. 



3. Polar Lights in Shetland. — We are informed by our former 

 pupil Mr Mouat Cameron, that the Polar lights had been un- 

 commonly frequent and brilliant during the latter part of last 

 summer and during the whole of autumn. On the 15th of No- 

 vember they were most splendid, exhibiting an appearance 

 which the oldest man in the country had never witnessed. " I 

 can compare it,"" says Mr Cameron, " to nothing but the light 

 thrown out from a foundry at work, supposing the horizon to 

 represent the mouth of the furnace — and even this conveys but 

 a feeble idea of its appearance." The Polar lights, we may add, 

 have been very frequent and brilliant in this neighbourhood. 

 This atmospheric luminous meteor appears, for these some years 

 past, to be running through one of its maximum periods. 



4. Nitrous Atmosphere of Tirhoot. — Tirhoot is one of the 

 principal districts in Indi^ for the manufacture of saltpetre ; 

 the soil is every where abundantly impregnated with this sub- 

 stance, and it floats in the atmosphere in such quantities, 

 that, during the rains and cold weather, it is attracted from 

 thence by the lime on the damp walls of houses, and fixes 

 there in shape of long downy crystals of exceeding deli- 

 cacy. From damp spots it may be brushed off every two 

 or three days almost in basketsful. In consequence of all 

 this, the ground, even in hot weather, is so damp, that 

 it is extremely difficult either to get earth of sufficient te- 

 nacity to make bricks (the country being quite destitute of 

 stones), or, when made, to find a spot sufficiently solid to sus- 

 tain the weight of a house. Even with the greatest care the 

 ground at last yields, and the saltpetre corrodes the best of the 

 bricks to such a degree, that the whole house giadually sinks 

 several inches below its original level. Houses built of inferior 

 materials, of course suffer much more; one, of which the inner 

 foundations were of unburnt bricks, absolutely fell down whilst 

 I was at Mullye, and the family in it escaped almost by miracle. 

 My own house, which was not much better, sank so much, 

 and the walls were at bottom so evidently, giving way, that I 



OCTOBER DECEMBER I8r30. M 



