CONTENTS. Ixxt 



That cold precedes the formation of dew ascertained by ex- 

 periment '- 1 %* .... page 182 

 This fact applied to explain several natural appearances. 



1. The variety in the quantities of dew on different bodies, 

 exposed to the air during the same time of the night, 

 but in different situations . . * 185 



2. The cold connected with dew, not being always pro- 

 portional to the quantity of that fluid . . ib. 



3. The production of heat by the formation of dew 186 



4. The fact of more dew being acquired, in very calm 

 nights, by substances placed upon a raised board, than 

 by others of the same kind on the grass ; and that of 

 a slight agitation of the atmosphere, when very preg- 

 nant with moisture, increasing the quantity of dew 



188 



5. The fact of dew never being formed in temperate 

 climates upon the naked parts of a living and healthy 

 human body . . . L3lv;j ?'? 189 



6. The fact of hygrometers, formed of animal and vegeta- 

 ble substances, when exposed to a clear sky at night, 

 marking a degree of moisture beyond what is actually 

 resident in the atmosphere . . .190 



The cold which produces detv, is itself produced by the radia- 

 tion of heat, from those bodies, upon u>hich deiu is deposited 



191 



The cold produced by the radiation of heat from substances 

 upon the surface of the earth, is compensated or over- 

 balanced in the day-time by the heat from the sun, and 

 lessened at night by various causes . .196 



The cold originating in the nightly radiation of heat from 

 bodies upon the surface of the earth, though lessened by 

 various causes, is often very considerable . .198 



Some of the useful effects of the radiation of heat from the 

 earth at night . : ,'. . . . ^ ,, 201 



Observations upon, or explanations of the under-mentioned 

 circumstances. 



