CHAP. 2. 21. OP EVAPORATION. 113 



are liable to be misled, and to mistake imagin- 

 ation for truth ; while the only resource of 

 the philosopher is to arm himself with their 

 mutual contradictions and common want of evi- 

 dence, and, retracing the steps of his wandering, 

 to sneak back into the plain regions of simple 

 observation, and content himself to behold the 

 variety and order of phaenomena.* 



* Dew is vapour condensed into visible drops. Under 

 whatever circumstances of diminished barometrical pressure or 

 decreased heat the air cannot hold so much water in solution 

 as before, the result must be a deposition of it in aqueous 

 particles ; during day and under some other circumstances of 

 electricity, definite and floating clouds are the result, and the 

 processes of Rain often commence; but in fine weather, in the 

 evening, the Vapour Plane being destroyed, and the nubific 

 principle ceasing to act, the vapour so deposited comes down 

 in Dew. The Dew is not the result always of the stratus, and 

 it differs from the wet mist of the cirrostrativeness of the 

 lower atmosphere. The circumstances under which Dew is 

 most plentifully formed being treated of by Dr. Wells, in his 

 Essay on Dew, I refer the reader to that publication, and 

 also to Bertholon's Elect. Met. 



