666 THE POPULAR SCIENCE MONTHLY. 



For 1871 the total rainfall was 52.06 inches, distributed as follows: 



During the first quarter 10.33 inches. 



" " second 11 14.12 " 



" third " 14.21 " 



" " fourth " 13.40 " 



Total 52.06 inches. 



So far as these years are concerned, there does not appear any evi- 

 dence of a decrease ; on the contrary, in the last there is a very consid- 

 erable excess over either of the others. 



Extending our examination to preceding years, as far bach as the 

 beginning of 1836, and grouping those years into three periods, each 

 of ten, and one of six years, the statement comes to this : 



First period from 1835 to 1846 39.5 inches. 



Second " " 1845 to 1856 47.0 " 



Third " " 1855 to 1866 52.0 " 



Fourth " " 18G5 to 1872 52.0 " 



This would make the annual rainfall, throughout these thirty-six 

 years, 47.62 inches. That of the last three years is 47.06 inches. 

 These numbers being substantially the same, it may be concluded that, 

 though there are large variations from year to year, these on the 

 whole will neutralize one another, when very long periods of time are 

 considered. 



In the foregoing table the numbers from 1836 to 1854 inclusive 

 are derived from the observations made by the military officers at 

 Fort Columbus, New York Harbor ; those for the next twelve years 

 are from the records of Prof. Morris in New York City ; and the re- 

 mainder are from the registers of this observatory. It is, of course, 

 assumed that the rainfall at Fort Columbus, that in New York City, 

 and that in the Central Park, are the same an assumption which, I 

 suppose, is under the circumstances admissible. 



The amount of rainfall not only influences in a predominant man- 

 ner the growth of plants, and therefore agricultural pursuits, deter- 

 mining the profitable cultivation of many different crops, it also exerts 

 an influence on several manufacturing operations. If, therefore, the 

 aboA r e statement be correct, no apprehension need be entertained of a 

 permanent disturbance in these particulars. Although in the last 

 38 years great changes have been made in all those portions of 

 the United States intervening between the Mississippi and the Atlantic 

 Ocean, large surfaces having been cleared of the primeval forest, and 

 brought under cultivation, their physical character and aspect having 

 therefore been essentially altered, no corresponding diminution can 

 nevertheless be traced in the mean amount of water that has fallen. 

 On the contrary, there has been an actual increase. It appears, there- 

 fore, that the wide-spread public impression, that the clearing of Ian 

 diminishes the volume of rain, is not founded on fact, and in trutl 



