7HEO RT of RAIN. 6 



for the production of rain ; and, idly, That there is, in the 

 conftitution of this terraqueous globe, caufes for mixing the 

 different parts of the atmofphere, particularly, during fummer, 

 or by the influence of the fun. Had the rule, eftablifhed 

 by nature, for the evaporation of water and condenfation of 

 vapour, followed any other ratio than that which has been in- 

 veftigated in the theory, no mixture of the atmofphere could 

 have produced either mift or rain, and the regions of conden- 

 fation muft have been limited to the regions of cold, 'where, in 

 all probability, there muft have been continual rain, with no 

 other variation, perhaps, than a little change in the limits of 

 the condenfing regions, each of thefe two regions increafing and 

 diminifhing alternately, with the feafons of winter and fummer. 

 IN the a<5lual fyftem of the globe, the cafe is different, and 

 there is ample provifion made, in general, for rain ; but, in 

 the theory which has been given with regard to a certain part 

 of that fyftem, there is required, for the production of rain, 

 certain circumftances and conditions which do not flow imme- 

 diately from the heating and cooling caufes exerted every 

 where upon the globe. If thofe conditions, therefore, are not 

 obferved in certain places, no rain fhould there appear, not- 

 withftanding the nature and fituation of fuch places mould be 

 fimilar to thofe of other places where abundant rain is found. 

 But, if it be reafohable to conclude, that, in fome particular 

 fituations, there fhould not be found the proper conditions for 

 mixing together portions of the atmofphere, fufnciently fatura- 

 ted with humidity, and in different degrees of heat, or that 

 thefe fhould occur but feldom, then, in finding upon the 

 whole earth precifely fuch a fpot or two, in which feldom or 

 very rarely it is found to rain, we might be allowed to fuppofe 

 a failure in the conditions proper for rain in thofe places ; and 

 to conclude this from the effect, where it is not poffible to fee 

 farther into the caufe. 



THE 



