VOL. XLII.J PHILOSOPHICAL TRANSACTIONS, 585 



pully ; then rubbing the glass with his hand during its motion, there appeared 

 a great deal of light of a purple colour within the globe, without any light or 

 attraction observed on the outside of the glass, which is observed when the air 

 has not been pumped out. Then turning the cock, so as to re-admit the air 

 gently into the globe during its motion, the light was broken and interrupted, 

 diminishing gradually," till at last it appeared only on the outside of the glass, 

 where it was accompanied with attraction. Does it not appear, that at first 

 the external air by its resistance drives back the electric effluvia, which go 

 then to the inside of the globe, where there is the least -resistance? for we ob- 

 serve, that as the air comes in, it repels the electric effluvia, that go inwards no 

 longer, when all the air is come in. If the fact be so, as the experiment shows, 

 is not my conjecture proved, viz. that the air is electrical ? 



In Dr. Hales's Vegetable Statics, several of his experiments show, that air is 

 absorbed, and loses its elasticity by the mixture of sulphureous vapours, so that 

 4 quarts of air in a glass vessel will be reduced to 3. Will not this phenomenon 

 be explained by the different electricity of sulphur and air ? The effluvia of sul- 

 phur, being electric, repel each other; and the particles of air, being also 

 electric, likewise repel each other. But the air being electrical, of a vitreous 

 kind, and sulphur of a resinous, the particles of air attract those of sul- 

 phur, and the moleculse compounded of them, becoming non-electric, lose 

 their repulsive force. 



It has for a great while been thought, that watery vapours, that rise in air to 

 form clouds, used to rise, because the water which is of itself specifically heavier 

 than air, being formed into little hollow spherules or bubbles filled with an aura, 

 or thinner air than the ambient air, in this new state made a fluid of little shells, 

 specifically lighter than the ambient air in which it must rise. But philosophers 

 have rejected that opinion ; and such as have implicitly come into it, may find 

 it refuted in the Philosophical Transactions, N° 407. 



Now may not this phenomenon of the rise of vapours depend upon electri- 

 city in the following manner ? The air which flows at top of the surface of the 

 waters is electrical, and so much the more as the weather is hotter. Now in 

 the same manner as small particles of water leap towards the electric tube, may 

 not those particles leap towards the particles of air, which have much more 

 specific gravity than very small particles of water, and adhere to them ? Then 

 the air in motion having carried off the particles of water, and driving them 

 away as soon as it has made them electrical, they repel each other, and also the 

 particles of air. This is the reason that a cubic inch of vapour is lighter than a 

 cubic inch of air; which would not happen, if the particles of vapour were only 

 carried off in the interstices of air, because then a cubic inch of air, loaded with 



VOL. viu. 4 F 



