THE LAW OF SUBSTANCE. 467 



THE LAW OF SUBSTANCE. 



By Professor R. H. THURSTON, 



CORNELL UNIVERSITY. 



IN Haeckel's new and remarkable monistic book, 'The Eiddle of the 

 Universe at the Close of the Nineteenth Century/ which has just 

 been translated by Joseph McCabe and published by the Harpers, the ac- 

 cepted laws of the persistence of matter and the persistence of energy 

 are enunciated and their unity insisted upon; the union constituting 

 what is denominated 'The Law of Substance/ Substance, 'Stoff/ in 

 other words, being in fact what we are familiar with as matter, includ- 

 ing all its physical attributes, as essential parts of it, as a person's char- 

 acter and his material parts are one and, failing either of those attri- 

 butes, is no longer the same. It is only by these characteristics that we 

 can recognize or define either the person or the molecule; without them, 

 so far as we can see, there would be neither person nor matter. 



The principle and the law of substance are unquestionably now in- 

 corporated into the scientific code permanently and positively; but the 

 time of recognition and the dates of discovery of the two elements of 

 that law are not, in the opinion of the writer, precisely as stated by 

 Haeckel; the discoverers are not given credit by this author in correct 

 proportion. He accords to Lavoisier the discovery of the persistence of 

 matter and the proof of that principle, undoubtedly, as generally be- 

 lieved, correctly. He gives Eobert Mayer (1842) credit for the dis- 

 covery of the principle of the persistence of energy and assigns to Helm- 

 holtz (1847) its more general application. 



It was, in fact, Benjamin Thompson (Count Bumf ord), the American 

 philosopher, who, in 1796-97, experimentally proved the equivalence of 

 the two forms of energy, thermal and dynamic. He read the paper de- 

 scribing his work in 1798, before the Eoyal Society of Great Britain; 

 while Sir Humphry Davy confirmed it and added further proof im- 

 mediately afterward. 



It must be carefully noted that there are at least three quantities to 

 be observed, studied and quantitatively measured: (1) substance or mat- 

 ter; (2) the forces which affect matter; (3) energy. Matter can perhaps 

 be conceived of as destitute of any designated force and possibly even of 

 any known attributes, such as the physical forces; forces can possibly 

 be conceived apart from any specific matter; energy involves both mat- 

 ter and motion, and infers the action of forces in its production or varia- 

 tion. Nevertheless, our only method of acquiring a knowledge of mat- 



