THKORY. 



lo the former fafts is totally intufficient. Long previous to 

 tlie true caufe of thofe*liniited doles, the fafts were fo coiifpi- 

 cuous, that a decided nomenclature was adopted for the pur- 

 pofe of exprelling thefe difTereut Rages ot combination. The 

 oxyds have been dillinguiflied by the Greek numerals prol, 

 ilait, tr'it. Sec. The falts containing two dofes of acid have 

 been cMed fuper-falts ; and thofe containing an extra dofe of 

 bafe, have been ca\\edful)-Jhl/s. 



Although chemills have frequently ufed a language which 

 appeared to Ihew their acquaintance with the real caufe of 

 the definite proportions, fuch as one compound being forced 

 by one proportion, dofe, or particle uf one of its elements, 

 and another with two proportions, dofes, or particles : on 

 the other hand, we find exprcfllons which would favour the 

 idea of indefinite proportions ; fuch as bodies lofing a 

 fmall portion of their oxygen, or abforbing a little oxygen 

 from the atmofphere. Salts are foraetimes faid to contain a 

 flight excefs of acid, or a fmall excefs of bafe. 



The moll decided language ufed in any chemical work 

 before the difcoveries of Mr. John Dalton, giving any idea 

 that the dofes are limited bv diftinct atoms, will be found in 

 a work by Mr. Higgins, entitled " A Comparative View of 

 the Phlogiftic and Antiphlogiftic Theories." We beg leave 

 to correal a miftake in a former article, in which we have 

 entitled this work a Treatife on Phlogifton. 



This work was written for the exprefs purpofe of com- 

 batting the phlogiftic theory, and principally in anfwer to 

 Mr. Kirwan's treatife of phlogifton. In order to fhew the 

 <;ontradiclions and abfurdities of the phlogiftic doftrine, 

 which, under the name of phlogifton, confounded a number 

 of bodies which were very different, he exhibited by 

 <5iagrams a number of chemical operations, in which he 

 liippofed the elementary bodies concerned to be ultimate 

 particles, and their immediate compounds molecules. He 

 in the fame diagrams alfo ufed numbers, which he fuppofed 

 to be eftimates of the ftrength of affinity of the combin- 

 ing particles. By this means he very fuccefsfuUy fhewed 

 many of the inconfiftencies which muft be admitted to 

 explain the phenomena on the phlogiftic theory. In this 

 mode of proceeding, however, the numbers exprelling the 

 relative attraftions, ferved his purpofe much more than the 

 :onfideration of the proportions being caufed by diftiniS 

 r.toms ; and the language which would induce the belief 

 that he had fucli a conception of the nature of elementary 

 matter, occurs only in a very few parts of his work. 



After concluding that it is unneceflary to admit the ex- 

 iftence of the imaginary fubftance phlogifton in fulphur, he 

 concludes, in page 36, that fulphurous acid is compounded 

 of one ultimate particle of fulphur with one of oxygen, 

 and that fulphuric acid confifts of one of fulphur and two 

 of oxygen. 



In the fame page he alfo obferves, that water is formed 

 by one ultimate particle of water united to one of oxygen. 



In page 81, he fuppofes fulphuretted hydrogen to confift 

 of nine ultimate particles of fulphur with five of hydro- 

 gen. Previous, however, to this conchifion, he believes 

 that the fulphur and hydrogen are not chemically combined, 

 but that the fulphur is dilTolved in hydrogen, as a fait dif- 

 folves in water. 



After ufing arguments to ftiew , in anfwer to Mr. Kirwan, 

 that the nitric acid does not contain what was thought to be 

 phlogifton, he concludes, in page 132, with giving what he 

 conceives to be its conftituents, «/2. that the nitrous oxyd 

 confifts of one ultimate particle of azote and one of oxygen ; 

 litrous gas, of one of azote and two of oxygen ; red ni- 

 trous vapour, one of azote and three of oxygen ; ftraw- 



coloured nitrous acid, one of azote to four of oxygen; and 

 laftly, that the nitric acid is conftituted by one of az.ote and 

 live of oxygen. Tliefe fafts are certainly very remarkable, 

 as they agree with the conclufions in the prcfent time, and give 

 a ftrong proof of Mr. Higgins's genius at the time he wrote. 



He does not, liowever, lay any llrefs upon thefe remai'ks, 

 and was not probably aware that they would be confirmed 

 by future refearch. We are induced to think fo, from the 

 manner in which he exprefles himfclf in other parts of his 

 work, in which he frequently fpeaks of the abforption of 

 fmall portions of oxygen, and of bodies having a fmall 

 portion of oxygen more than tliey can retain. This vague 

 manner of fpeaking, and others which we do not immediately 

 recolleift, is fuflicient to fliew that Mr. Higgins had no 

 fixed notions of the caufe of definite proportions, and that 

 the language in which he has ufed the words ultimate par- 

 ticles and molecules, was employed rather with a view to 

 illuftrate his examples, than to broach any new theory to 

 explain indefinite proportions. Indeed it would have been 

 inconfiftent to have treated two fubjefts, fo very different in 

 their objefts, in the fame pages. 



As a proof that there was nothing ftriking in the remarks 

 in which the words ultimate atoms and molecules are men- 

 tioned, we only need refer to the article which Mr. Hig- 

 gins himfelf quotes from the Analytical Review, written 

 foon after the appearance of the work in queftion. The 

 reviewer gives him the higheft praife for the able manner in 

 which he lias refuted the doftrine ot phlogifton, but does not 

 even hint at his diagrams or the ultimate particles. Indeed 

 we can venture to aftert, that if no more had been faid on 

 the fubjeft of definite proportions than is to be found in 

 this work, w» might yet have been as much in the dark 

 as we were twenty years after the publication of Mr. Hig- 

 gins's " Comparative View." 



It was not enough to know that compound bodies were 

 formed of particles, to enable us to explain the caufe of 

 definite proportions ; and we waut no greater proof of this, 

 than the faft of the true caufe not being known till twenty- 

 eight years after Mr. Higgins liad told us that one particle 

 of fulphur and one of oxygen formed fulphurous acid, 

 and that one to two formed fulphuric. acid. Thefe 

 loofe expreflions v/ere but a fmall ftep indeed tow.irds the 

 difcovery of the atomic theory in its prelent form, which 

 has placed chemiftry on the fame ground with that on 

 which the difcovery of the laws of gravity placed the 

 fcience of aftronomy. 



We are inclined to believe that the firft ftep towards this 

 important difcovery was given by Richter. He found, 

 in the double decompofition of falts, that the acid of one 

 fait was always juft fufficient to faturate the bafe of the 

 other, and •vice' verfd. He alfo afcertained, that when one 

 metal was precipitated by another, the oxygen of the pre- 

 cipitated metal was juft what was required by the preci- 

 pitating metal. 



The inference to be drawn from thefe fafts was, that 

 if A combine with .v to faturation, and B with y to the 

 fame ; then, if A ihould be found to faturate y, B 

 would alfo faturate x. This inference may be ftill further 

 extended ; for if A be a body capable of combining -with 

 B, they will mutually faturate each otlier. 



It is the means of drawing thefe inferences arifing from 

 the mutual fitnefs of thofe parts of bodies which combine, 

 that conftitutes the importance of the atomic theory, and it 

 is for the eftablilhment of this new principle that we are in- 

 dcbtedy to Mr. John Dalton. When Mr. Higgins can 

 Ihew, ftom the data given in his work, that fimilar infer- 



euce* 



