[_Where lighter gases_. l. 123. Mr. Cavendish has shewn that the gas called inflammable air, is at least ten times lighter than common air; Mr. Lavoisier contends, that it is one of the component parts of water, and is by him called hydrogene. It is supposed to afford their principal nourishment to vegetables and thence to animals, and is perpetually rising from their decomposition; this source of it in hot climates, and in summer months, is so great as to exceed estimation. Now if this light gas passes through the atmosphere, without combining with it, it must compose another atmosphere over the aerial one; which must expand, when the pressure above it is thus taken away, to inconceivable tenuity. If this supernatural gasseous atmosphere floats upon the aerial one, like ether upon water, what must happen? 1. it will flow from the line, where it will be produced in the greatest quantities, and become much accumulated over the poles of the earth; 2. the common air, or lower stratum of the atmosphere, will be much thinner over the poles than at the line; because if a glass globe be filled with oil and water, and whirled upon its axis, the centrifugal power will carry the heavier fluid to the circumference, and the lighter will in consequence be found round the axis. 3. There may be a place at some certain latitude between the poles and the line on each side the equator, where the inflammable supernatant atmosphere may end, owing to the greater centrifugal force of the heavier aerial atmosphere. 4. Between the termination of the aerial and the beginning of the gasseous atmosphere, the airs will occasionally be intermixed, and thus become inflammable by the electric spark; these circumstances will assist in explaining the phenomena of fire-balls, northern lights, and of some variable winds, and long continued rains. Since the above note was first written, Mr. Volta I am informed has applied the supposition of a supernatant atmosphere of inflammable air, to explain some phenomena in meteorology. And Mr. Lavoisier has announced his design to write on this subject. Traite de Chimie, Tom. I. I am happy to find these opinions supported by such respectable authority.]