First then, in page 130. Mr. Eeles has asserted, that the greatest possible rarefaction of water is when it boils. I think 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; so 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. In page 133. 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), I know no experiment to show it. If it be meant, that it is capable of being attracted to a greater distance; I conjecture it may, as the heat will rarefy the ambient air, and we know the electric æther is attracted at very great distances in _vacuo_; but this cannot properly be called an increased activity of electric fire. We are afterwards told (page _ib._) “that electric fire will not mix with air:” whence, in the succeeding section, it is argued, “That as each particle of vapour, with its surrounding 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 thro’ 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 thro’ air, and, I am persuaded, 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 cieling 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, thro’ the oil into the air above, high electricity was given. The oil did not appear at all to subside: whence I conclude, 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.