ASTRONOMY. 249 



*.ir is eight hundred and fifty times less than that of water, so that one 

 gallon of air will weigh a little less than one seventh of an ounce. This 

 air we are constantly inhaling by the action of the lungs, which air 

 expanding by the vital heat is expelled, and the vacuum supplied by a 

 fresh inhalation. It is therefore evident, that air too much rarified is 

 not proper to sustain animal existence, and that air too much condensed 

 is alike unsuited for that purpose ; therefore, any effluvia raised or 

 imbibed, that tends to impregnate the air with vapours, or atoms of a 

 strange or tmusual kind, even though of an odoriferous and agreeable 

 scent, is unwholesome ; plants as well as animals will decline under 

 the influence of vitiated air. The whole expanse filled with the fluid 

 called air, or which we denominate the atmosphere, is the region or 

 reservoir of the winds; those winds being the floating streams that run 

 in currents from the surcharged, towards the exhausted parts of the 

 spacious void. Wherever the air becomes rarified, or the moisture of 

 its composition diminished, to that part will it rush with a force equal to 

 the weight by which it is impelled, and that weight will be in exact 

 preponderancy of the circumambient element over the specific gravity 

 of the space rarified. Heat, as has been just observed, is the cause of 

 this phenomenon; for, in fact, heat engenders motion, and motion excites 

 heat, so that there is a perfect reciprocity of influence. 



The component parts of air, or the atmosphere, cannot be positively 

 defined, because we cannot describe that which is invisible; we discover 

 fire and water as the chief ingredients, but what other elements of 

 nature more subtile than fire may exist we do not know ; the electric 

 fluid, though acting on combustible bodies, is perhaps only the agent that 

 provokes the flame, and carries with it, or collects the fire that invests 

 the surrounding space; but there is a magnetic quality in the electric 

 fluid, that indicates something of nature yet undiscovered; there may 

 be a distant element in this irresistible force of motion. Fire will not 

 naturally adhere to indurated bodies, it requires violent and continued 

 motion to infuse its particles, and to make it separate the atoms of iron ; 

 but lightning instantly decomposes that substance, and reduces it to a 

 state of fusion. It seems likely from this experimental process, that an 

 element more penetrating and keener than fire prevades the universe, 

 and another still on ad infinitum. Air is indestructible: that is, you 

 cannot change its nature, it will still be air under whatever process you 

 may place it, you cannot make it any thing else ; but its quality may 

 alter, and it is subject to perpetual changes, such as hot, cold, moist, and 

 dry; these are variations, but only in the effect that it produces according 



