THE EARTH. 147 



CHAPTER XXI. 



OF METEORS, AND SUCH APPEARANCES AS RESULT FROM A COMBINATION 

 OF THE ELEMENTS. 



IN pioportion as the substances of nature are more compounded 

 and combined, their appearances become more inexplicable and 

 amazing. The properties of water have been very nearly ascertain- 

 ed Many of the qualities of air, earth, and fire, have been discovered 

 and estimated ; but when these come to be united by nature, they of- 

 ten produce a result which no artificial combinations can imitate ; and 

 we stand surprised, that although we are possessed of all those sub- 

 stances which nature makes use of, she shows herself a much more 

 various operator than the most skilful chymist ever appeared to be. 

 Every cloud that moves, and every shower that falls, serves to mor- 

 tify the philosopher's pride, and to show him hidden qualities in air 

 and water, that he finds it difficult to explain. Dews, hail, snow, and 

 thunder, are not less difficult for being more common. Indeed, when we 

 reflect on the manner in which nature performs any one of these 

 operations, our wonder increases. To see water, which is heavier 

 than air, rising in air, and then falling in a form so very different 

 from that in which it rose ; to see the same fluid at one time descend- 

 ing in the form of hail, at another in that of snow ; to see two clouds 

 by dashing against each other, producing an electrical fire, which no 

 watery composition that we know of can effect ; these, 1 say, serve 

 sufficiently to excite our wonder ; and still the more, in proportion as 

 the objects are ever pressing on our curiosity. Much, however, has 

 been written concerning the manner in which nature operates in these 

 productions; as nothing is so ungrateful to mankind as hopeless ig- 

 norance. 



And first, with regard to the manner in which water evaporates, 

 and rises to form clouds, much has been advanced, and many theories 

 devised. All water,* iay some, has a quantity of air mixed with it ; 

 and the heat of the sun darting down, disengages the particles of thk 

 air from the grosser fluid : the sun's rays being reflected back from 

 the water, carry back with them those bubbles of air and water, 

 which, being lighter than the condensed air, will ascend till they 

 meet with a more rarefied air ; and they will then stand suspended. 

 Experience, however, proves nothing of all this. Particles of air or 

 fire, are not thus known to ascend with a thin coat of water ; and in 

 fact we know the little particles of steam are solid drops of water. 

 But besides this, water is known to evaporate more powerfully in the 

 severest frost, than when the air is moderately warm.t Dr. Hamilton, 

 therefore, of the university of Dublin, rejecting this theory, has en 

 deavoured to establish another. According to him, as aquafortis is a 

 menstruum that dissolves iron, and keeps it mixed in the fluid ; as 

 aquaregia is a menstruum that dissolves gold ; or as water dissolves 

 salts to a certain quantity ; so air is a menstruum that corrodes ana 

 lissolves ?. certain quantity of water, and keeps it suspended above. 



Spectacle de la Nature, vol. iii. 4- Memoires de ('Academic des Sciences, an. 1705 



