104 M. Boussingault on the Effects of' clearing Land 



at the wheels. Two years of hydrometrical observations are 

 sufficient even in the tropics to exhibit the variation in the an- 

 nual quantity of rain ; and the observations at Marmato esta- 

 blish that the mass of running water has diminished at the very 

 time that the quantity of rain had increased. 



It is then probable that local clearings of no great extent may 

 diminish the copiousness of springs and rivers, and even cause 

 them to disappear, and under circumstances where these effects 

 can in no degree be attributed to a diminution of the fall of 

 rain. 



Finally, We have still to examine if the extensive clearing of 

 forests, extending over considerable districts, has any effect in 

 making the rain less copious .? In reply, we remark, that it is 

 only hydrometrical observations that can lead to the solution of 

 this question. And unfortunately the observations of this sort, 

 which might be at our command, do not reach back far enough ; 

 and, so far as Europe is concerned, they were not commenced 

 till the whole clearing process was well nigh over. The United 

 States of America, however, where the forests are disappearing 

 with astonishing rapidity, may perhaps supply the required data 

 at no distant period. 



In studying the phenomena of rain under the tropics, I have 

 at length formed, in connection with this question of clearing, a 

 very decided opinion, which I have freely communicated to 

 many. I regard it certain, then, that a very extensive clearing 

 diminishes the annual quantity of rain which falls upon a coun- 

 try. 



It has long ago been remarked, that, in equinoctial regions, 

 the epoch of the rainy season returns every year with astonish- 

 ing regularity. This is most true ; whilst at the same time 

 this meteorological fact ought not to be announced in terms too 

 general. There is the greatest possible regularity in the al- 

 ternation of we', and dry seasons, in those countries whose terri- 

 tory is very much varied. Thus, a country which at once ex- 

 hibits forests and rivers, mountains and great plains, lakes and 

 extensive table lands, will at the same time exhibit periodic 

 or changing seasons with a regularity which is quite remark- 

 able. This, however, is no longer true if the territory be more 

 uniform, and if it become in any way peculiar. The epoch of 



