56 Translation ofRey's Essat/s. 



step further, and add, that if the simple heat of the sun thits 

 thicken our lower air, and make it heavier, driving upwards its 

 more subtle parts, and keeping the denser and more solid 

 (drues) below, what will not the vehement and long-continued 

 heat from the, mouth of a red-hot furnace effect? A quantity 

 of brandy placed over it in a vessel will disappear, common 

 water, and all sorts of liquors, will exhale in a few hours. 1 he 

 air nevertheless will remain there, (there being no other body 

 to fill its place) but it will be an air of the utmost possible den- 

 sity and weight; an air, as I may say, no longer air, but that 

 has lost its nature, having changed its subtle fluidity for a vis- 

 cid grossness, (grossicretc visqueiise.) For the violence of the 

 fire, subtilizing all the air that comes near it, will drive an im- 

 mense quantity of it to a distance, leaving around itself, of this 

 immense quantity, only a kind of dregs, which from its gluti- 

 nous weight cannot fly off. 



Essay XII. 



Fire, by its heat, can thicken homogeneous Bodies. 



I know not what fatal calamity has seized the sciences, that 

 when an error has arisen in them, and they are, as it were, inured 

 to it by time, their professors will not endure its abatement. The 

 doctrine of the preceding essay has already been taken in dudgeon, 

 (forniuUse) Bind it has been objected to me, that since fire thickens 

 heterogeneous bodies, by separating their more sybtle parts, as 

 being of a different nature, it cannot do the same with homo- 

 geneous bodies, inasmuch as it acts uniformly on all their parts, 

 and has no other action than that of distending and dilating 

 them equally ; so that, on this account, air_^cannot be thickened 

 and made heavy by the force of heat. I recognise this doc- 

 trine, (thus opposed to my belief,) as derived from the school 

 of philosophers, whom I honour for their great insight into 

 nature ; but I frankly avow, that I have never sworn by the 

 words of any of them. If truth be with them, I receive it;— 

 if not, I seek it elsewhere. Let us see if they have met \vith it 



