72 THEORY cf RAIN. 



are to be confidercd in relation to the perceived effects, rain or 

 drought, which are fuppofed to happen in confequence of one 

 or more of thofe three caufes ; that thus we may endeavour to 

 difcover which of thefe is to be efteemed the proper caxife, and 

 which to be conlidered as only a concomitant appearance. 



NOTHING appears to us fo diftinct as the motion and direction 

 of the wind, yet nothing is fo fallacious as the reafoning from 

 this appearance, confidered as a caufe in the changes to be pro- 

 duced in the atmofphere, and as explaining thofe effects of 

 change which we perceive. In making our obfervations on the 

 wind, we are limited to a fpot, which may be confidered as a 

 point in the line of the wind's direction ; and, from our obfer- 

 vations in this fpot, we are apt to conclude with regard to ope- 

 rations which include a great extent. When, for example, the 

 wind blows from the weft, in our obfervation, we fay, it has 

 come along the Atlantic ; when, from the eaft, that it has come 

 from the continent of Europe ; yet, unlefs we fuppofe the wind, 

 in moving, to preferve a ftraight line, or direct courfe, it muft 

 be evident, that, in thofe two cafes, the wind, inftead of 

 coming, as we imagine, from the eaft or weft, may truly 

 have come from the north or fouth. Now, to any one who 

 confiders attentively the nature of motions in the fluid at- 

 mofphere, it muft appear, that a ftraight line is that, of all 

 others, which there is the leaft reafon to conclude mould take 

 place in the variable winds of the globe ; but thefe are the 

 winds only with which we are now concerned. 



IT will likewife be evident how great a difference there is be- 

 tween a weft or eaft wind and a fouth wind, on the one hand, 

 or a north wind, on the other. Now, what a confufion, in our 

 reafoning, muft fometimes follow this prefumption of our 

 principles ? For, if we may confound a fouth wind, in our ob- 

 fervations, with a wind coming to us directly from the weft, 

 we muft alfo be fubject to miftake a north wind upon a like oc- 

 calion, ;. e. in taking it for a weft wind. Thus, therefore, in 



reafoning 



