Ixxii CONTENTS. 



1 . The prevention, wholly or in part, of cold from radia- 

 tion, in substances on the ground, by the interposition 

 of any solid body between them and the sky page 203 



2. The prevention, wholly or in part, of cold from radia- 

 tion, in substances on the ground, by the interposition 

 of clouds ", '';'- . . . . 205 



3. The prevention, wholly or in part, of cold from radia- 

 tion, by fogs . ... 207 



4. The prevention, wholly or in part, of cold from radia- 

 tion, by conduction from warmer substances in contact 

 with the radiating substance . . .211 



5. The effect of wind in compensating the cold from ra- 

 diation, and sometimes in lessening, and sometimes in 

 increasing the production of dew . . 212 



6. The cold from radiation, of a thermometer placed on a 

 board, being less diminished than that of one suspended 

 in the air ..... 213 



7. The hurtful effects of cold occurring chiefly in hollow 

 places, according to a remark of Theophrastus 214 



8. Frost being less severe upon hills, than in neighbouring 

 plains, in calm and serene nights . -<'.. 215 



Reasons assigned for believing that air is actually heated by 

 the sunbeams which enter it, and that it not only absorbs, 

 but radiates heat .... >/;. 217 



9. The leaves of trees often remaining dry throughout 

 the night, while those of grass are covered with dew 



227 



10. Bright metals exposed to a clear sky in a calm night 

 being less dewed on their upper surface, than other 

 solid bodies j and those metals which radiate heat most, 

 being most attractive of dew . . #?V 228 



11. The difference between black and white bodies with 

 respect to radiation, when exposed to the sky at night 



235 



Whether dew is the product of vapour emitted during the 

 night by the earth and plants upon it . . 236 



