124 Dr. E. J. Mills on the Atomic Theory. 



spoken of as familiarly as if they were fossils. The ingenuous 

 confession of Gregory is difficult to reconcile with his practice, 

 but it doubtless expresses the feeling of many atomists : " we may 

 admit the atomic theory. It is to be observed, however, that 

 we have no positive proof of its truth, nor are we likely to obtain 

 such proof P Of what use is it to serve a writ of habeas corpus 

 upon such a theory ? 



At this point my mind naturally recurs to a period in the 

 history of chemistry when the science was in one particular re- 

 spect under as anomalous a regime as prevails at present. From 

 about the year 1700 the belief in phlogiston prevailed for 

 three quarters of a century, and was as intimately associated 

 with experimental inquiries as the atom is now ; and this belief, 

 as any one who has read a fragment of the literature of that 

 epoch must have observed, was as real and living as can be con- 

 ceived. Yet, in 1764, Macquer* confesses, "Hitherto chy- 

 mists have never been able to obtain the phlogiston quite pure 

 and free from every other substance;" and Bishop Watson, in 

 1800 (1781 ?), with a somewhat ruffled dignity, exclaimsf, 

 " You do not surely expect that chemistry should be able to pre- 

 sent you with a handful of phlogiston separated from an inflam- 

 mable body ! " In course of time the nature of phlogiston 

 varied as much as the atomic weight of any modern element. 

 It began with being materia vel principium ignis, non ipse ignis, 

 and ended with a narrow escape from identification with hydro- 

 gen. It was as material as Lavoisier's caloric. Yet chemists 

 argued universally, and apparently by preference, without any 

 quest of the substance itself. How the native freedom of an ex- 

 perimental science could coexist in the same person with so 

 marvellous an abrogation of that freedom was long a puzzling 

 phenomenon to me. The phlogistian, however, is much sur- 

 passed by the atomist. The former never ascribed to his veiled 

 companion an attribute without natural analogy ; but the latter 

 teaches Tertullian's paradox, Certum est, quia impossibile. 



When a great system, instead of reposing on clearly ascer- 

 tained facts, is built upon the sands of fancy, its history must, 

 as a rule, be a record of feeble instability. What has been the 

 case with chemical theory so far as it has been atomic ? The 

 absolute, unalterable carbon atom has weighed 6, 3, and 12 ; 

 that of oxygen was 8 a few years since, now it is 16; but a con- 

 temporary chemist proposes to return to the old number. At 

 first the atoms are introduced with radiant rods or lines of at- 

 traction ; then these appendages appear to have become super- 

 fluous, for we hear nothing of them for many years ; now they 

 are to be seen on numerous lecture-tables, are treated of in most 

 * Traite, i. p. 10. f Essays, i. p. 167. 



