Correspondence. . 279 



ness) "dusty theory," and as shewing the influence of moisture in 

 clearing the air. 



Also in Kimedy, which is not more than sixty miles from the sea- 

 shore, the air is generally beautifully clear, the climate being usually 

 very damp and when the air was dry it was generally hazy. Now 

 if I remember correctly, these changes sometimes occurred at intervals 

 of only two or three days, whereas you will observe that had dust been 

 the cause of the haze, it ought also to have produced the same effects in 

 damp weather. 



But I don't intend to draw you into a fruitless argument, but only to 

 make good the "possibility" of a cause I have suggested. If we set to 

 work to argue upon first causes upon the imperfect data which have 

 been collected on the subject of Meteorology, we shall be as bad as some 

 geologists, cosmogsists as they ought rather to be termed. 



While in Kimedy, I observed a curious phenomenon, which has been 

 remarked upon, I think, by Saussure on Mont Blanc, which was, that 

 at night, during the very damp and cold weather, the sky in the zenith 

 was more like black than blue, and the stars looked like " pantiles of 

 burnished gold set on black velvet." I would quote Poetry, but am 

 nearly as bad as Marryatt's light Prose. The sky about the horizon, or 

 rather near the tops of the surrounding mountains, was more of a decid- 

 ed blue than in the zenith. 



While upon this subject, I recollect a curious instance of the extreme 

 clearness of the air, I should perhaps call it tenuity, on the 15th of 

 November 1834, at Ooplauda. Venus was plainly visible to the naked eye 

 at 12 o'clock, two hours from her meridian passage, day clear and sun- 

 shine strong ; and again on the 18th November at 2 o'clock she was again 

 plainly visible. At this time I think it is stated, that Venus was not at 

 her greatest brilliancy. I am not aware that Venus has ever been seen 

 in the same way, at least I have never seen it mentioned any where, and 

 I have never seen the planet since in the same way. 



I do not find any note of why I sought for the planet ; but think 

 it was on account of the extreme clearness of the air. 



The star could not be seen unless the eye was directed exactly to the 

 place, which I did by a little three inch Kater's circle, with a telescope 

 magnifying seven times, having computed the azimuth and altitude for 

 the time. After having seen the star through the telescope, I observed, to 

 my surprize, that I could still see it on looking over the telescope, and on 

 calling a servant, and pointing carefully and exactly with my finger, he 

 saw it also, and became so excited with delight, that not content with 

 shewing it to all the other servants, the lad ran off to point it out to 

 others ; and in a few minutes every one in the place was staring at Venus. 



