Erasmus Darwin, Tr. by W.S. Dallas

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879. Excerpt: ... et csetera. Therefore I suppose that atmospheres of heat of different densities, like atmospheres of electricity, will repel each other at certain distances, like globules of quicksilver pressed against each other, and that hence by applying a heated body near one end of a cold body, the more distant end may immediately become colder than the end nearest to the heated body. March 11, 1784. Since I wrote the above I have reconsidered the matter, and am of opinion that steam, as it contains more of the element of heat than water, must require more absolute cold to turn it into ice, though the same sensible cold, as is necessary to freeze water, and that the phenomenon you have observed, depends on a circumstance which has not been attended to. When water is cooled down to freezing point, its particles come so near together, as to be within the sphere of their reciprocal attractions;--what then happens?--they accede with violence to each other and become a solid, at the same time pressing out from between them some air which is seen to form bubbles in ice and renders the whole mass lighter than water (on which it will swim) by this air having regained its elasticity; and pressing out any saline matters, as sea-salt, or blue vitriol, which have become dissolved in it; and lastly by thus forcibly acceding together, the particles of water press out also some more heat, as is seen by the rising of the thermometer immersed in such freezing water. This last circumstance demands your nice attention, as it explains the curious fact you have observed. When the heat is so far taken away from water, that the particles attract each other, they run together with violence, and press out some remaining heat, which existed in their interstices. Then the contrary must also t...