PART I. 

 OF A REMARKABLE LAW 



WHICH HAS BEEN FOUND TO OBTAIN IN THE CONDENSA- 

 TION OF WATER WITH COLD, WHEN IT IS NEAR THE 

 TEMPERATURE AT WHICH IT FREEZES ; AND OF 

 THE WONDERFUL EFFECTS WHICH ARE PRO- 

 DUCED BY THE OPERATION OF THAT 

 LAW IN THE ECONOMY OF NATURE. 



TOGETHER WITH 



CONJ ECTURES 



RESPECTING THE FINAL CAUSE OF THE SALTNESS OF 

 THE SEA. 



CHAPTER I. 



Danger of admitting received Opinions in Philosophical In- 

 vestigations without Examination. — The free Passage of 

 Heat, in all Bodies^ in all Directions^ never yet called in 

 ^estion. — Heat does not, however, pass in this Manner 

 in all Bodies without Exception. — Air and Water, and 

 probably all other Fluids, are, in fact, Non-Conduc- 

 TORS OF Heat. — Accidental Discoveries which led to an 

 experimental Investigation of this curious Subject. — The 

 internal Motions among the Particles of Fluids rendered 

 visible. — The Propagation of Heat in Fluids obstructed 

 and retarded by everything which obstructs the internal 

 Motions of their Particles ; hence there is Reason to conclude 

 that Heat is propagated in them only in Consequence of 

 those Motions, — that it is transported by them, not suffered 

 to pass through them. — Furs and Feathers, and all 

 other like Substances, which, in Air, form warm Covering 

 for confining Heat, found, by Experiment, to produce the 



