LABORS OF THE JOINT COMMITTEE. 161 



From an Essay on Meteorological Observations, by J. N. Ni- 

 collet, Esq., written in compliance with a wish expressed to 

 him by the Honorable J. R. Poinsett, Secretary of the De- 

 partment of War, I quote a few interesting paragraphs, 

 as being peculiarly appropriate here. 



THE FORMATION OF CLOUDS. 



130. There is a certain kind of cloud which forms only 

 in the day, when the heavens are not overspread with other 

 clouds, and when the dew point is not too low, which, when 

 well formed, generally appears with a broad dark base, and 

 narrow top, something in the form of a cone, with sides as 

 white as snow. There is no cloud ever seen below the base 

 of this cloud, but it frequently rises with its top above the 

 highest clouds, which it pierces with its snow-white top. 

 As it passes through the uppermost or feathery cloud, it 

 seems to lift the thin cloud before it, and condense it into a 

 semi-transparent veil, which at first appears at some distance 

 above the top of the columnar cloud; but finally as the col- 

 umnar one moves upwards, its well defined top reaches the 

 thin veil and penetrates it. Very soon afterwards by the 

 upward motion of the columnar, the veil coalesces with the 

 columnar cloud, and can no longer be distinguished from it. 

 The same phenomena frequently take place, when no fea- 

 thery clouds are to be seen in the higher strata of air. When 

 the top of the columnar cloud reaches a great elevation, it 

 is seen to form above it, at a short distance, a similar veil 

 or cap, which it gradually overtakes and coalesces with, as 

 before mentioned. The bases of these clouds are probably 

 all on the same horizontal level ; and if the theory which 

 has been lately advanced in the Journal of the Franklin In- 

 stitute is correct, the height of these bases, is as many hun- 

 dred yards as the temperature of the air is above the dew 

 point, at the moment of observation, in degrees of Fahrenheit. 

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