4SH Notes on the Injkience [No. 



tunately the observations of this sort which might be at our com- 

 mand, do not reach back far enough and, so far as Europe is con- 

 cerned, 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 ai 

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

 decided opinion, which I have freely communicated to many. I re- 

 gard it certain, then, that a very extensive clearing diminishes the 

 annual quantity of rain which falls upon a country. 



It has long ago been remarlsed, that, in equinoctial regions the 

 epoch of the rainy season returns every year with astonishing regu- 

 larity. This is most true, whilst at the same time this meteorologi- 

 cal fact ought not to be announced in terms too general. There is 

 the greatest possible regularity in the alternation of wet and dry 

 seasons in those countries whose territory is very much varied. 

 Thus a country which at once exhibits 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 remarkable. This, however, is no longer true if the territory 

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

 of the return of the rainy season will be much less regular if the face 

 of the country be exposed and arid ; also if cultivation to a great ex- 

 tent has partially taken the place of forests ; and finally if the rivers 

 are numerous, the cultivation be but limited, then the irregularity of 

 the seasons will still manifest itsejf, but with quite a different charac- 

 ter. Rain will then predominate, and in some years it will become, 

 so to speak, continual. 



The continent of America presents to us, in immense extent, two 

 regions which are placed under the same conditions as to temperature, 

 and in which we successively meet those circumstances which are the 

 most favourable to the formation of rain and those which are of directly 

 opposite character. In leaving Panama, and traveUing towards the 

 south we pass the Bay of Cupica the provinces of San BuenaVantura, 

 of Choco, and of Esmeraldas. In this country, covered with thick 

 forests, and furrowed by a multitude of rivers the rains are almost un- 

 ceasing. In the interior of Choco, no day passes without rain. On 



