VIII. Answers to the Objections of M. DE Luc with regard 

 to the Theory of Rain. By James Hutton,M.D. 

 F. R. S. Edin. and Member of the Royal Academy of Agri- 

 culture at Paris, 



{Read by the Author y Dec. 3. 1787. J 



MDe Luc, in his Idee s fur la Meteorologie, has made 

 • fome objections to the Theory of Rain * which I had 

 the honour to lay before this Society. I lhall now endeavour 

 to anfwer thefe objections ; and hope the Society will forgive 

 me for taking up a little of their time and attention with this 

 fubject. The reputation of M. de Luc is fo well eflablifhed in 

 the republic of letters, that I muft not neglect remarks which 

 have the fanction of fuch authority ; although, in the prefent 

 cafe, they appear to me to have come from a judge who was too 

 much preoccupied with a different fyftem. 



The queftion between us, according to M. de Luc's own 

 ftatement, is this> Whether or not, when two mafTes of air of 

 different temperatures are mixed together, the humidity of the 

 new mafs is greater than the mean between the humidities 

 which the two maffes had feparately ? This I maintain to be a 

 phyfical truth, and M. de Luc refufes to admit it as a rule in 

 nature. 



I had eflablifhed this propofition, That, upon the fuppofition 

 of the evaporating power increafing with heat, but increaflng 

 at a greater rate, the mixture of two portions of air, of different 

 temperatures and fuflkiently faturated with humidity, would 

 produce a condenfation of water which might then become vi- 

 able., 



* Tranfaftions of the Royal Society of Edin. Vol.1. N° II. Phyf. CI. 



