xl INTRODUCTION. 



on the summit of the mountain becomes turbid, the cloud is shortly formed, 

 and, hurried by the wind over the verge of the precipice in large fleecy vol- 

 umes, rolls down the steep sides towards the plain, threatening momentarily 

 to deluge the town. No sooner, however, does it arrive in its descent at 

 the point of temperature equal to that of the atmosphere in which it has 

 floated over the isthmus, than it is once more taken up, arid 'vanishes into 

 air to thin air.' " [John Barton. Tilloch, vol. x. p. 225. 



The doctrine of concussion producing condensation of aqueous vapor, has 

 no foundation in nature. It is surprising to me, that Mr. Barton should not 

 have known the principle, that cold, by the expansion of the air as it ascends 

 the sides of mountains, is sufficient to produce condensation. It is a principle 

 long familiar to the scientific world, and it is one which I used in my early 

 writings, as belonging to the great storehouse of science, as common proper- 

 ty, without even inquiring who was the original discoveier, or who first saw 

 a cloud form in the receiver of an air pump on extracting the air. Mr. H. 

 Meikle claims this discovery as original. So far as I am concerned, he shall 

 never be deprived of that honor; I lay no claim to it. (See Appendix, 

 page 547.) 



Facts communicated by Simeon Borden, Esq., of Boston. " In the western 

 part of the state of Massachusetts, there are many mountains of considerable 

 elevation. Amongst them I have spent much time in the course of three or 

 four years just past. The following phenomena are of almost every day oc- 

 currence : 



" One day, as I was standing near the base of the Watatick mountain, (a 

 mountain about two thousand feet in height,) looking at the clouds, which 

 were apparently resting upon its top at that time, the wind was blowing 

 briskly from some southerly point; the day was remarkably pleasant, the 

 sun shone brilliantly, and the cloud which capt the mountain was not large, 

 I observed frequently, upon the windward side of the mountain's top, that 

 many square yards of transparent atmosphere would occasionally become 

 suddenly transformed into a dense fog or cloud, which would then pass with 

 the current of the atmosphere across the top of the mountain, and would then 

 as suddenly vanish into transparent atmosphere again, resembling in its 

 transformation, very much in form or shape, that of a vanishing flame of fire. 

 1 noticed at other times, that although the wind would frequently be blowing 

 briskly, still tho cloud would apparently remain stationary upon the moun- 

 tain top ; sometimes it would however appear to enlarge, and then again 

 would diminish, and pretty uniformly in fair weather would rise from and 

 leave the mountain top entirely near midday." 



