that all that makes it significant for chemical practise is expressible in this way: If any two substances unite with each other chemically, they do so in such a manner that there are no particles of them so small as not to follow the same law of combination that holds for the substances in bulk.
Atoms in modern chemistry are small bodies imagined to constitute visible substances, and they are imagined for the purpose of incarnating, if you will, the observed trait that substances have of combining with one another according to known rules. As to most of the other properties of atoms, their shape, color, hardness, etc., if atoms are conceived to be anything else than little particles of the substances, science knows no more to-day than did Newton and Democritus.
The purpose of this little excursion into the atomic doctrine, that border-land of physical science, is to bring home something of the mighty power there is in the properties of things, and in sense experience. It is not too much to say that the modern science of chemistry was born then and there, when one property that substances have, viz., that of definite combination with other substances, was attached to the hitherto purely speculative, more or less mystical atoms of those substances.
I ask you now to recall what was said about the way we deal with the salt, sodium and chlorine. Substantially the statement was that we have to treat them all on exactly the same basis, so far as the process of knowing is concerned. That is, we have to treat each one on the basis of its own properties. We can not touch sodium with our knowledge of the properties of chlorine, nor vice versa. Similarly, we can not touch sodium with our knowledge of the properties of salt, nor salt with our knowledge of the properties of sodium, except, mark you, as we may say that one property of sodium is its power to unite with chlorine to produce salt. My familiar expression for this is that the external world and our minds are so constituted, are so articulated with each other, that every object in that world must be treated on its own merits. Now notice that since these substances must be treated, each on its own merits, and since the sodium and chlorine have the power of combining with each other in such a remarkable way that they wholly lose their original properties, at least temporarily, and merge into another substance, salt, with properties wholly its own, we must recognize that the properties of substances manifest something of transitoriness and relativity.
Thus are we led to the notion which I have ventured to speak of as the standardization of reality. The expression is suggested by the chemist's process of standardizing solutions; the process, that is, of using a solution of known composition and concentration as a unit of value to which to refer various reactions and processes. The meaning is that whatever criterion of reality you apply to any natural object,
