176 Of Pneumatics'.

extinguishes flame, and destroys life. Th edreadful effects of damps are sufficiently kno^nto such as work in mines.

If part of the vivifying spirit of air in 3°/country begins to putrefy, the inhabitants of thatcountry will be subject to an epidemical diseasf*which will continue until the putrefaction lSover. And as the putrefying spirit occasion Sthe disease, so if the diseased body contributetowards the putrefying of the air, then the dis*ease will not only be epidemical, but pestilentialand contagious.

The atmosphere is the common receptacleall the effluvia or vapours arising from differentbodies; of the steams and smoke of things burntor melted; the fogs or vapours proceeding fron 1damp watery places; and Of the effluvia fro# 1sulphureous, nitrous, acid, and alkaline bodies*In short, whatever may be called volatile, risein the air to greater or less heights, accordingto its specific gravity.

When the effluvia, which arise from acid andalkaline bodies, meet each other in the ah*there will be a strong conflict or fermentation bC'tween them ; which will sometimes be so great*as to produce a fire; then if the effluvia becombustible, the fire will run from one p 3 rtto another, just as the inflammable matter hap'pens to lie.

Any one may be convinced of this, by mixingan acid and an alkaline fluid together, as tl> espirit of nitre and oil of cloves; upon the doingof which, a sudden ferment, with a fine flatn e *will arise; and if the ingredients be very p ureand strong, there will be a sudden explosion.Thunder Whoever considers the effects of fermenta-and light- tion, cannot be at a loss to account for the*>ӣ. dreadfn*

Fermenta-

tions.