of the Cumulus Cloud. 137 



similar clouds formed, but they were more broken and irregu- 

 lar. At one time, when the morning mist had been raised, 

 say apparently 100 or 150 yards above the surface, a most 

 beautiful view was presented. An indefinite number of thin 

 clouds seemed to be hung vertically in the air, of various de- 

 grees of transparency, with spaces intervening, so as to give 

 a sufficiently distinct view of the lower part of each film of 

 cloud. The whole looked like an immense hall with a mix- 

 ture of glass and thin muslin drapery suspended in the upper 

 part, the particular appearances changing every few minutes. 

 Between these vertical films of cloud there appeared to be 

 slight tremulous upward movements of the air, similar to those 

 which are seen over heated sands or over the top of a hot 

 stove, indicating that there were ascending currents of air in 

 those places. Similar appearances were presented at other 

 times, but they were less clear. 



In watching such scenes, one of the most striking circum- 

 stances presented to the notice is the formation of the cumu- 

 lus cloud. It takes so definite a form, has such an uniformity 

 of character, appears so plainly to grow up before your eyes, 

 and ascend from the surface of the land or water to a consi- 

 derable elevation in the heavens, and is so grand in its appear- 

 ance, that it becomes invested with a peculiar interest. The pre- 

 vailingopinion which has existed for a long time past respecting 

 the formation of clouds has, I believe, been, that they resulted 

 from an intermixture of different currents of air, and that the 

 small particles of water which constitute the cloud, notwith- 

 standing appearances, do not in reality rise in opposition to 

 the laws of gravity. But any one who will take the trouble 

 to watch the formation of the cumuli over the Irish Sea, say 

 from eight to twelve o'clock in the morning, towards the lat- 

 ter end of summer, will find it difficult to resist the conviction 

 that they really do rise in the atmosphere. The same identi- 

 cal mass of cloud may often be distinctly traced from the sur- 

 face of the sea until it passes over your head at a considerable 

 elevation ; and the swelling prominences of the upper part of 

 the cloud when seen in profile are so like in shape and motion 

 to those which may be seen in smoke issuing from a chimney, 

 or in steam when escaping from a boiler, as to induce an im- 

 pression that similar causes produce all the effects. Mr. Espv, 

 in his lectures recently delivered in this town, professed to 

 account for the formation of "the Cumulus;" but some gen- 

 tlemen think he did so in an unsatisfactory manner, it there- 

 fore seems desirable that his theory should be subjected to the 

 test of an examination. This gentleman (Mr. Espy) says, 

 that the sun when it rises increases the temperature of that 



