PROFESSOR OLMSTED'S OBJECTIONS. 443 



gelation, even if it was saturated from that point to the top 

 of the atmosphere, which it never is, would not make one 

 inch and a half of rain if it were all condensed. Now, in 

 moderately cold weather, one of two things is certain, either 

 a very large portion of a storm cloud must be above the 

 region of congelation, where there is but little vapor to con- 

 dense, or if not, then is the perpendicular diameter of the 

 cloud, from its base to its summit, so small that the stratum 

 of air of that thickness, can furnish but a very minute 

 quantity of vapor to form cloud. 



It supposes that the air in a summer day, when thousands 

 of cumuli form, mingles hot with cold, and forms clouds in 

 the form of sugar loaves, with flat bases, all on the same 

 level with intervening spaces, where there is no mingling, 

 without assigning any reason why it should mingle in that 

 shape with the bases on the same level, and their tops at 

 different heights. It supposes that this mingling goes on, 

 without saying whether it is done by air coming down from 

 above, and mixing with air below, or whether currents 

 meet in a thousand different directions on the same hori- 

 zontal level, or how there can be so many "patches" of 

 cold and warm air in the neighborhood of each other, or 

 why they rush into each other's embraces without any 

 imaginable cause. 



If it is supposed that the cloud is formed by a current of 

 cold air coming down " from the regions of perpetual frost," 

 and mingling with the warm humid air below, if it pro- 

 duced cloud on this principle, it would not be likely to stop 

 till it reached the surface of the earth ; and the cloud would 

 be hollow, for the internal parts of the descending current 

 could not mingle with the surrounding air, and there would 

 then be an outward motion of the air in all directions, at 

 the surface of the earth, from the centre of the descending 

 current, which is contrary to known facts. If the cloud is 

 supposed to form by an ascending current mingling with 



