62 'THE OR T of RAIN. 



THE lower Egypt, and a narrow fpot upon the coaft of Peru, 

 are the only examples that we have of this fingular occurrence. 

 It would have been impoflible, a priori, to have concluded, that, 

 of all the places upon the earth, thefe two fhould have been thofe 

 in which rain fhould not happen ', the knowledge of man, in 

 tracing future effecls from known caufes, will ever be, perhaps, 

 too imperfect for fuch an undertaking, where it is necefTary, 

 not only to value every condition neceffary in the data, but al- 

 fo every quantity and degree in thofe different conditions ; but, 

 though we may not form that judgment a priori, yet, finding 

 that thefe are the only places in which rain does not fall, we 

 may be allowed to conclude, that fuch is the natural flate of 

 the winds about thofe places, as to prevent the proper conditions 

 for producing rain. 



This conclufion is alfo, in fome meafure, confirmed from 

 ULLOA'S obfervations with regard to the wind, which appears 

 to blow fo fleadily upon the coafl of Peru, that either continual 

 rain might be here expected, or no rain at all, upon this coaft. 

 In this laft cafe, we would have reafon to conclude, that the va- 

 pours from the fea were carried over the coaft to be condenfed, 

 by mixing with other ftreams of cold atmofphere in the moun- 

 tainous regions of the Andes, where it rains fo abundantly for 

 moft part of the year. 



IF, on the one hand, we fuppofe the wind blowing conti- 

 nually from the fea, without mixing with a ftream of air pro- 

 per to condenfe humidity, it muft pafs over this heated coaft, 

 without letting fall a drop of rain. If, on the other hand, we 

 {hall fuppofe the trade- wind, which has come over the Atlantic, 

 to be continued over the ridge of the Andes, weftward, after 

 having depofited much rain in this hilly region, there would 

 be alfo no reafon to fuppofe, that this current of atmofphere, 

 pafling over the heated coaft, fhould there find conditions pro-? 

 per for condenfing its humidity. 



BUT 



