CO Mr. Henry on the Confijlency of 
fupply, to the more fuperficial inquirer, much 
indrudtion and entertainment. Every man is 
intereded in the properties of a fluid to which he 
is fo intimately related, and without which, he 
cannot fubfid a moment. Its various degrees of 
gravity, elafticity, heat, moiflure, and purity, 
all affe£t the human race. Many of the mod 
dire difeafes which afflifl mankind, are occafioned 
by noxious impregnations of the atmofphere, or 
cured by more favourable dates of it. And 
many of the operations of nature and art are 
eflfentially influenced by the changes which are 
Continually occurring in it. 
Philofophy has lately made mod rapid ad¬ 
vances in difcovering the conditution of com¬ 
mon air. The ingenious Dr. Priedley has even 
taught us the art of fabricating it artificially, of 
producing it in a degree of purity far exceeding 
that of the mod falubrious climate, and of re¬ 
ducing it to the date in which we commonly breathe 
it when debafed by exhalations from the various 
bodies which it lurrounds. From him we have 
alfo learned a mode of judging of the different 
degrees of purity in air, by means of the 
eudiometer, as of its gravity and heat by the 
barometer and thermometer. This excellent 
philofopher, to whom, as a learned foreigner 
has obferved, <c Nature takes delight in revealing 
her fecrets,” has alfo fird difcovered, and Dr. 
Ingenhoufe, treading in his paths, has more 
completely 
