CHAPTER XVIII. 



DEW. 



's Journal. Baptists Port* nearly discovered the true theory of 

 dew. Thought dew was condensed from air. Aristotle thought it 

 was condensed from vapour. Muschenbrook kept back Meteorology 

 one hundred years. Great discoveries often foiled by the stupidity 

 of the world. Dr. Wells said to be the discoverer of the true dew 

 theory. The radiation of heat, the basis. The cause of moonblind- 

 ness. Dew forms most readily on vegetation. Arguments against 

 radiation. Observations with wool packs. Position everything. 

 Calm and clear evenings essential. Dew is water. Produced in a 

 similar way. The cause of fog and hoar frost. Hoar frost spears 

 of ice. 



IN "Chambers's Journal" for 1868, is an article on the 

 above subject, which pretends to settle the question definitely 

 About the formation and phenomenon of dew ; but, like most 

 other explanations of natural phenomena, it fails for want of a 

 correct apprehension of natural law. 



We find in it, that one Baptista Porta, nearly discovered, 

 (according to our view of it) the true theory of dew ; but his 

 notions arc; su.Tiv<l at altogether, because they do not agree with 

 dynamical principles. 



The old idea was, that dew was precipitated from the moon 

 and stars ; which also shed down cold. But the writer of the 

 above mentioned article states, that so far from shedding cold 



