in Fluids. 267 



principles, to render the passage of their Heat out of 

 them more difficult, and consequently to retard their 

 congelation. 



But there is still another circumstance, and a very re- 

 markable one indeed, which, if our conjectures respect- 

 ing the manner in which Heat is propagated in liquids 

 be true, must act a most important part in the preserva- 

 tion of Heat, and consequently of animal and vegetable 

 life, in cold climates. But as the probability of all these 

 deductions must depend very much on the evidence 

 which is brought to prove the great fundamental fact on 

 which they are established, that respecting the internal 

 motions among the particles of liquids which necessarily 

 take place when they are heated or cooled, before I pro- 

 ceed any farther in these speculations, I shall endeavour 

 to throw some more light on that curious and interest- 

 ing subject. 



CHAPTER II. 



Farther Investigations of the internal Motions among the 

 Particles of Liquids which necessarily take place when they 

 are heated or cooled. Description of a mechanical Con- 

 trivance^ by which these Motions in Water were rendered 

 visible. An Account of various amusing Experiments 

 which were made with this new-invented Instrument. 

 They lead to an important Discovery. Heat cannot be 

 propagated DOWNWARDS in Liquids, as long as they con- 

 tinue to be condensed by Cold. Ice found, by Experiment, 

 to melt more than eighty times slower when boiling-hot 

 Water stood on its Surface, than when the Ice was suffered 



