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The irreversible character of this process is strikingly embodied in Fourier's theory of the conduction of heat, where the formulae themselves indicate, for all positive values of the time, a possible solution which continually tends to the form of a uniform diffusion of heat.
For purposes of insulation the wires were neatly covered with cotton-yarn and then saturated in a bath of hot gum-shellac, but this treatment proved defective in insulating properties, for when ten miles of line had been completed the wires were found to be wholly useless for electric conduction.
Reliable determinations of the "energy" of the individual spectral rays were, for the first time, rendered possible by his invention of the "bolometer" in 1880. This exquisitely sensitive instrument affords the means of measuring heat, not directly, like the thermopile, but in its effects upon the conduction of electricity.
Clausius' and Maxwell's explanations of the diffusion of gases, and of thermal conduction in gases, their charmingly intelligible conclusion that in gases the diffusion of heat is just a little more rapid than the diffusion of molecules, because of the interchange of energy in collisions between molecules, while the chief transference of heat is by actual transport of the molecules themselves, and Maxwell's explanation of the viscosity of gases, with the absolute numerical relations which the work of those two great discoverers found among the three properties of diffusion, thermal conduction, and viscosity, have annexed to the domain of science a vast and ever growing province.
We are told by physiologists that stimuli applied to the nerves in certain cases induce contraction or motion in the muscles by direct conduction of a stimulus along a nerve, or by the conduction of a stimulus to a nervous centre, whence it is reflected along another nerve to the muscles.
Some years subsequently he answered this question by saying that the liquid condition enables the molecule of water to turn round so as to place itself in the proper line of polarization, while the rigidity of the solid condition prevents this arrangement. This polar arrangement must precede decomposition, and decomposition is an accompaniment of conduction.
It was shown that antimony did not conform in its reactions with at least one of the tests, which Professor Aiken said his precipitates did; that almost all the other reactions could be closely simulated with ordinary organic bodies; that the processes used were those universally condemned by authorities; and that carelessness was everywhere so manifest in their conduction as to entirely vitiate any results.
The line of observation which has led to the most striking results has to do, as already suggested, with the conduction of electricity through liquids and gases. It has long been known that many liquids conduct electricity with relative facility. More recently it has been observed that a charge of electricity carried by any liquid bears a curious relation to the atomic composition of that liquid.
In a champaign region insufficiently provided with natural channels for the discharge of the waters, and with a subsoil which, though penetrable by the roots of trees, is otherwise impervious to water, it is of cardinal importance; but though trees everywhere tend to carry off the moisture of the superficial strata by this mode of conduction, yet the precise condition of soil which I have described is not of sufficiently frequent occurrence to have drawn much attention to this office of the wood.
From this comparison of conducting power the important fact will appear that when any two of these metals are used in the same line of conduction, the one of low power should be proportionately larger.
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