128 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 75/. 



their present state of rarefaction ; and lastly, that clouds of particular shapes will 

 be sustained or elevated by the motion they acquire from winds. 



Mr. Eeles has asserted, that the greatest possible rarefaction of water is when 

 it boils. And it might be said, with equal propriety, that the greatest rarefaction 

 of solids, was when they began to melt : and this may indeed be verbally true, 

 if we chuse to alter the names of bodies, when they undergo any alteration by 

 fire : for solids take the name of fluids, when they are in fusion ; and water the 

 name of vapour, when it is greatly rarefied in the steam-engine. Whence we 

 find this assertion seems to be founded on a confusion in terms, and the fact far 

 from being existent in nature. 



He says also, the sphere of electrical activity is said to be increased by heat. If 

 by electrical activity is here meant an increase of its repulsive power (the thing, 

 which seems to be wanted in Mr. Eeles's hypothesis), there is no experiment to 

 show it. If it be meant, tliat it is capable of being attracted to a greater dis- 

 tance ; probably it may, as the heat will rarefy the ambient air, and we know 

 the electric aether is attracted at very great distances in vacuo ; but this cannot 

 properly be called an increased activity of electric fire. 



We are afterwards told that electric fire will not mix with air : whence, in the 

 succeeding section, it is argued, * That as each particle of vapour, with its sur- 

 ' rounding electric fluid, will occupy a greater space than the same weight of 

 * air, they will ascend.' In answer to this, it must be observed, that there are 

 some bodies, whose parts are fine enough to penetrate the pores of other bodies, 

 without increasing their bulk ; or to pass through them, without apparently 

 moving or disturbing them. A certain proportion of alcohol of wine mixed 

 with water, and of copper and tin in fusion, are instances of the first of these ; 

 the existence and passage of light through air, and probably of electric fire, are 

 instances of the second. 



To illustrate this, the following experiment was instituted. A glass tube, 

 open at one end, and with a bulb at the other, had its bulb, and half way from 

 thence to the aperture of the tube coated on the inside with gilt paper. The 

 tube was then inverted in a glass of oil of turpentine, which was placed on a 

 cake of wax, and the tube kept in that perpendicular situation by a silk line 

 from the ceiling of the room. The bulb was then warmed, so that, when it 

 became cold, the turpentine rose about half way up the tube. A bent wire 

 then being introduced through the oil into the air above, high electricity was 

 given. The oil did not appear at all to subside : whence he concluded, that the 

 electric atmosphere flowing round the wire and coating of the tube, above the 

 oil, did not displace the air, but existed in its pores. Hence it is evident, that 

 electric matter surrounding particles of vapour, must increase their specific 

 gravity, and cannot any- ways be imaginetl to facilitate their ascent. 



