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206 the development of their result. Four years have since elapsed, during which, the effects, if any, have been accumulating, and it is the object of this brief paper to give an account of them.

The point under consideration originally was, whether there existed any definite limit to the force of vaporization. Water at 220° sends off vapour so powerfully, and in such abundance as to impel the steam-engine; at 120° it sends of much less; at 40°, though cold, still vapour rises; below 32°, when the water becomes ice, yet the ice evaporates; and there is no cold, either natural or artificial, so intense as entirely to stop the evaporation of water, or in the open air prevent a wet thing from becoming dry.

The opinion of many, among whom were the eminent names of Sir H. Davy and Mr. Dalton, was, that though the power of evaporating became continually less with diminution of temperature, it never entirely ceased, and that therefore every solid or fluid substance had an atmosphere of its own nature about it and diffused in its neighbourhood; but which being less powerful as the body was more fixed, and the existing temperature lower, was, with innumerable substances, as the earths, metals, &c., so feeble as to he quite insensible to ordinary or even extraordinary examination, though in certain cases they might affect the transmission of electricity; or, rising into the atmosphere, produce there peculiar and strange results.

The object of my former paper was to show that a real and distinct limit to the power of vaporization existed, and that at common temperatures we possess a great number of substances which are perfectly fixed. The arguments adduced, were drawn first from the power of gravity, as applied by Dr. Wollaston, to show that the atmosphere around our globe had an external limit, and then from the power of cohesion; either of these seemed to me alone sufficient to put a limit to vaporization, and experiments upon the sufficiency of the latter force were detailed in the paper.

The conclusion was, that although such substances as ether, alcohol, water, iodine, &c. could not as such be entirely deprived of their vaporizing force, by any means we could apply to them, but, if in free space or in air, would send off a little vapour, yet there were other bodies, as iron, silver, copper,