116 



ball at the moment of a flash, although the lightning is several miles 

 distant. 



Prof. Bache gave an account of the formation of cumulus 

 cloud from the action of a fire, as witnessed by him in the 

 month of August last, at Ellicottville, in the state of New 

 York. 



The place where this phenomenon was observed is nearly sur- 

 rounded by hills ; the valley in which it is situated extending to the 

 southward. Near the foot of the hills on the north side of the village, 

 a fire was made of the heavy timber which had been felled in clear- 

 ing a small tract of land. The column of heated air from the fire, 

 made visible by the smoke and condensing vapour, rose almost verti- 

 cally, widening irregularly as it rose, curling over at the sides and 

 reaching various heights. On one occasion, when the height of the co- 

 lumn, judging from the known distance of the fire and the angle of 

 elevation, was about three-tenths of a mile, the top flattened out, 

 presenting a mushroom appearance. The smoke having been left 

 behind in the ascent of the heated air, the condensed vapour form- 

 ing the top of the column artd presenting precisely the appearance 

 of a cumulus cloud, was carried slowly to the westward; rising 

 gradually and at first enlarging itself, it next became feathery at 

 the edges, and finally disappeared. The lower current of air was 

 from the S. W., and moderate in force. An upper current, as 

 shown by the direction of the small cloud just described, was pass- 

 ing at a small elevation from the N. N. W. 



A second time a small cumulus cloud formed, at the distance of 

 about two hundred yards above the smoke from the fire, and without 

 visible connexion with it. This cloud enlarged in its ascent until, 

 when about the same height as the former cloud, it began to move 

 from the N. N. W. It next separated into two parts, one rising ra- 

 pidly, and in turn breaking into two portions; the whole three 

 small masses thus formed being carried slowly from the N. N. W., 

 and the two lower ones gradually disappearing. A detached cloud 

 of the same kind gradually formed to the leeward of the upper re- 

 maining one, presenting the general appearance, upon a small scale, 

 of the detached masses which may be seen to form in the neighbour- 

 hood of thunder clouds in the summer season. 



These observations were made on the 16th of August, between 

 1§ and 2 P. M. The temperature of the air was 80°, the evaporating 

 point 64°, and the height of the barometer 28.74 inches. From these 



