by Dmitri Mendeleev
Translated from the Russian by George Kamensky (Imperial Mint, St. Petersburg), Longmans, Green & Co, NY (1904)
In his Dictionaire Complet, P. Larousse defines the Aether as ‘an imponderable elastic fluid, filling space and forming the source of light, heat, electricity, etc.’ This is laconic, but sufficient to raise some misgivings in the mind of a thoughtful man of science. He is obliged to admit, in the ether, the properties of a substance (fluid), while at the same time, in order to explain in some way the transmission of energy through space by its motion, the ether is assumed to be an all-pervading ‘medium’.
Moreover, in order to explain the phenomena of light, electricity, and even gravity, this medium is supposed to undergo various disturbances (perturbations) and changes in its structure (deformation), like those observed in solids, liquids and gases. If the fluid medium permeates everything and everywhere, it cannot be said to have weight, just as the ponderability of air could not be recognized before the invention of the air pump. Yet the ether must have weight, because, since the days of Galileo and Newton, the quality of gravitation or of weight forms a primary property of substances.
From various considerations Lord Kelvin came to the conclusion that a cubic meter of ether should weigh about and not less than 0.000,000,000,000,000,1 gram, while a cubic meter of the lightest gas, hydrogen, weighs 90 grams under the atmospheric pressure. The above-mentioned misgivings of the thoughtful scientist in his most plausible endeavors to ascribe a certain weight or mass to the ether, for the question naturally arises: At what pressure and temperature will this weight be proper to ether?
For at infinitely small pressures or exceedingly high temperatures steam or hydrogen would have as small a density as that given by Lord Kelvin for the ether. And as regards the density of the ether in interplanetary space, neither steam nor hydrogen would have a measurable density in these regions, notwithstanding the extreme cold, for the pressure would be infinitely small.
Theoretically, space may be supposed to be filled with such rarified residues of vapors and gases. And this view even corresponds with Kant’s and LaPlace’s and other theories, which strive to explain the unity of plan in the creation of the heavenly bodies. It also accounts for the uniformity of the chemical composition of the entire universe, demonstrated by the spectroscope, as it gives a means, through the agency of such ether, of interchange between the heavenly bodies.
One of the objects of an investigation into the elasticity or compressibility of gases under low pressure, undertaken by me in the 1870s, was to trace, as far as the then existing methods of measuring low pressures permitted, the changes proceeding in gases under low pressures. The discrepancies from Boyle’s law observed (by me and M. Kirpitchnikoff, 1874) for all gases, and subsequently confirmed by Ramsay and others (although still denied by some investigators), indicate a certain uniformity in the behavior of all gases and a tendency in them towards a certain limiting expansion at low pressures, just as there is a limit to compression (liquefaction and the critical state).
But determinations of very low pressures are accompanied by insurmountable difficulties. It proved practically impossible to measure, with any degree of accuracy, pressures under tenths of a millimeter of mercury, and this is far too large a figure for such rarified media as are supposed to exist at an elevation of even 50 kilometers above sea level. Hence the conception of the ether as a highly rarified atmospheric gas cannot so far be subjected to experimental investigation and measurement, which alone can direct the mind in the right direction and lead to reliable results.
But, beyond this, the conception of the ether as a limiting state of expansion of vapors and gases cannot sustain even the most elementary analysis, for ether cannot be understood otherwise than as an all-pervading ubiquitous substance, and this is not the property of either gases or vapors. Both the latter are liquefiable under pressure, and cannot be said to permeate all substances, although they are widely distributed in mature, even in meteorites. Moreover — and this is the most important — they vary infinitely in their chemical nature and in their relations to other substances, while the ether, as far as is known, is invariable. Owing to the variety of their chemical properties, all vapors and gases should react differently on the bodies which they permeate if they were components of the ether.
Before proceeding further, I think it necessary to justify the chemical views here and elsewhere brought into play. In the days of Galileo and Newton it was possible, although difficult, to conceive ether apart from them. But now it would be contrary to the most fundamental principles of natural science, for chemistry, since Lavoisier, Dalton and Avogadro Gerhardt, has acquired the most sacred rights of citizenship in the great company of the natural sciences, and by placing the mass (weight) of a substance among its paramount conceptions it has followed the path indicated by Galileo and Newton.
Moreover, chemistry and its methods alone have promoted in science a desire to apprehend bodies and their phenomena in their ultimate relations, through a conception of the reaction of their infinitely small parts or atoms which may in fact be regarded as indivisible individuals, having nothing in common with the mechanically indivisible atoms of the ancient metaphysicians.
There are many proofs of this; it will suffice to mention the fact that the atoms of modern science have often been explained by vortex rings, that there was formerly a strong inclination to conceive the chemical atoms as built up of themselves, or of a ‘primary matter’, and that recently, especially in speaking of the radioactive substances, a division of chemical atoms into yet smaller ‘electrons’ begins to be recognized; all of which would be logically impossible were the atom regarded as mechanically indivisible.
Chemically the atoms may be likened to the heavenly bodies, the stars, sun, planets, satellites, comets, &c. The building up of molecules from atoms, and of substances from molecules, is then conceived to resemble the building up of systems, such as the solar system, or that of twin stars or constellations, from these individual bodies. This is not a simple play of words in modern chemistry, nor a mere analogy, but a reality which directs the course of all chemical research, analysis, and synthesis.
Chemistry has its own microscope for investigating invisible regions, and being an archi-real science it deals all the time with its invisible individualities without considering them mechanically indivisible. The atoms and molecules which are dealt with in all provinces of modern mechanics and physics cannot be other than the atoms and molecules defined by chemistry, for this is required by the unity of science. And therefore the metaphysicians of the present day should, for the advancement of knowledge, regard atoms in the same sense as that in which they are understood by natural science and not after the manner of the ancient metaphysicians of the Chinese or Greek schools.