Meteorological Observations at Hudson, Ohio. 325 



from the west, and in the northern hemisphere generally from a 

 point a little south of west. This seems to indicate that the 

 mean progress of the upper half of the atmosphere is from south 

 to north, which being admitted, it follows of necessity that the 

 mean progress of the lower half is from north to south, and by 

 the same quantity. If it should be found that in particular lon- 

 gitudes the mean progress of the entire atmosphere is from south 

 to north, there must be other longitudes where there is a com- 

 pensation. 



The following table exhibits the proportion of the different 

 varieties of clouds, the number under each month being the sum 

 of the observations for the three years. 



In my classification of the clouds, I follow the nomenclature of 

 Howard, rejecting one of his divisions, the nimbus. I do not 

 perceive from Howard's description, that the nimbus differs from 

 some of his other varieties, except in the fall of rain, a circum- 

 stance, as appears to me, not sufficiently characteristic to form 

 the basis of a separate variety. Clouds sometimes undergo a 

 decided change as rain begins to fall, but the contrary is also of 

 frequent occurrence. During a large part of the winter season, 

 the sky at this place is overcast with a sheet of cloud so uniform 

 and unbroken, that it is with the utmost difficulty the least mo- 

 tion in it can be detected. From such a bed, flakes of snow fre- 

 quently fall day after day in such slow succession as not sensibly 

 to increase upon the ground; nor do the clouds sensibly change 



