APPENDIX TO THE METEOROLOGICAL JOURNAl.* 143 



The upper gauge, No. 1, is fixed on the N. W, angle of O'^servations 

 , , , .on rain and 



a glass turret, or observatory, on the house top, having a rain gauges. 



small vane and a conducting rod a few feet to the S. and 



S. E., but no other commanding object near it. The whole 



of the amounts of rain given in the tables in the Athenceurn 



during 1807, 1808, and part of I8O9, were obtained with 



this gauge. The gauge No. 2, the products of which I 



now prefer to register, is placed on a grass plot, about 70 



feet from the west front of the house. Their difference in 



elevation is about 43 feet. 



It appears, from the total result of these observations, 

 that about one'fourth of the rain which fell in twenty days 

 was formed within 50 feet of the Earth's surface. 

 . In attending to the manner in which the rains fell, the 

 cause of the frequent difference in the products of the 

 gauges, was, at times, obvious. When they were alike, the 

 abundance and active appearance of the clouds in the 

 higher atmosphere, together with the transparency of the 

 lower, indicated that the whole supply might very well be 

 derived from above. On the contrary, in several cases of 

 excess in No. 2, the lower air was very turbid, showing that 

 the decomposition of vapour was going on quite down to 

 the surface of the Earth ; or, in other words, that the rain- 

 ing clouds, though not distinguishable as aggregates to us, 

 who were enveloped in them, actually swept, or rested upon 

 that surface. 



On the first day, when the products were 5* 'S, the mean 

 temperature was lowered 6% probably by the effect of the 

 gentle easterly current, which decomposed the vapour 

 near the surface. On the 28th of the tenth month, when 

 the results were large and equal, a southerly current ap- 

 pearetl to prevail in the region of the clouds, with, probably, 

 a N. W. wind above it; by which the vapour coming from 

 the south was decomposed. This was accomplished at a 

 distance from the Earth, and the mean temperature was 

 lowered 1°, These two cases may elucidate the phenome- 

 non without a long train of reasoning. 



If we admit, that a portion of the atmosphere, contiguous 

 to the Earth's surface, may be so cooled by a superior por- 

 tion moving in a different direction, or with different velo- 

 city 



