THE EARTH. 315 



hot bar of iron into a vessel of water, the fluid 

 rises, and large drops of it fly up in all manner 

 of directions, every part bubbling and steaming 

 until the iron be cold. Why may we not, for a 

 moment, compare the rays of the sun, darted 

 directly upon the surface of the water, to so many 

 bars of red-hot iron ; each bar, indeed, infinitely 

 small, but not the less powerful ? In this case, 

 wherever a ray of fire darts, the water, from its 

 repulsive quality, will be driven on all sides ; and 

 of consequence, as in the case of the bar of iron, 

 a part of it will rise. The parts thus rising, 

 however, w r ill be extremely small, as the ray that 

 darts is extremely so. The assemblage of the rays 

 darting upon the water in this manner, will cause 

 it to rise in a light thin steam above the sur- 

 face ; and as the parts of this steam are extreme- 

 ly minute, they will be lighter than air, and con- 

 sequently float upon it. There is no need for 

 supposing them bubbles of water filled with fire ; 

 for any substance, even gold itself, will float on 

 air, if its parts be made small enough ; or, in 

 other words, if its surface be sufficiently in- 

 creased. This water, thus disengaged from the 

 general mass, will be still further attenuated and 

 broken by the reflected rays, and consequently 

 more adapted for ascending. 



From this plain account, every appearance in 

 evaporation may be easily deduced. The quan- 

 tity of heat increases evaporation, because it raises 

 a greater quantity of steam. The quantity df 

 wind increases evaporation ; for, by Waving the 

 surface of the water, it thus exposes a greater 



