250 



NINTH ANNUAL REPORT OF 



In the 67 rains which furnished an opportunity of observing the upper 

 cloud, its course was as follows : 



Northeast * 1 



North and northwest 7 



West 16 



Southwest 23 



South 14 



Southeast 6 



These results concur with observations made in the Atlantic States, 

 showing that the higher strata of atmosphere which sweep northward 

 from the equatorial i-egion, saturated with aqueous vapor, are the prin- 

 cipal source of rain in the temperate latitudes. 



In the following table is recorded the number of days in each month 

 on which clouds were observed in the lower and higher strata of atmo- 

 sphere, the first column referring to the lower clouds, and the second 

 to the higher. In the other columns is noted the direction of the higher 

 clouds, as far as observed. The direction of the lower clouds, which 

 mostly move with the wind near the earth's surface, is omitted. 



The higher cloud was, in the majority of cases, a light cirrhus, often 

 very partial, or seen only in the horizon, and composed probably of 

 congealed vapor, at an elevation of two or three miles. In other cases 

 it was a cirro-cumulus, or a nimboid-cumulus. In almost every 

 month of the year, even during the dry season, the clouds put on the 

 appearance of rain and then vanish. It is evident that the phenomena 

 which produce rains in other climates are present in this, but not quite 

 in sufficient degree to accomplish the result, except during the rainy 

 season, and then only by paroxysms, with intervening periods of 

 drought. 



The tabic shows the presence of an upper cloud on 260 days of the 

 year 1851, and a lower cloud on 278 days. The lower cloud was 



