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LXVI. On Dr. Murray’s Statement respecting the Origin. of 
ihe Doctrine of Definite Proportions, and the Arrangement 
- of the Elementary Principles of Chemical Compounds. By 
WituiaM Hieerns, Esq. 
To Mr. Tilloch. 
Sir, — You will much oblige me by inserting in your Maga- 
zine, the following observations on an extract taken from the 
first volume of Dr. Murray’s System of Chemistry (page 127, 
Ath edition, 1819). 
“ In a work (says the Doctor) published by Mr. Higgins a 
number of years ago (A Comparative View of the Phlogistic and 
Anti-phlogistic Theories, with Inductions, 1789) some. cases of 
chemical compounds are stated, in which the chemical combina- 
tions are held to consist of one particle of the one body, with one 
particle, two particles, acy four, or five of another. [In sul- 
phurous acid a single particle of sulphur is supposed to be united 
with a single particle of oxygen, and in sulphuric acid with twe 
particles of oxygen:(page 36). Water is held to be composed of 
one particle of oxygen with one of hydrogen, and to be incapable 
of uniting to a third particle of either (page 37). In sulphu- 
retted hydrogen the particles of sulphur are supposed to be to 
those of hydrogen as nine to five * (page 81): and in the nitrous 
compounds he supposed one particle of nitrogen to be combined 
with two particles of oxygen,forming nitric oxide; one with three, 
constituting red nitrous acid ; one with four, constituting the pale 
yellow acid; and one with five, forming colourless nitric acid (page 
133-5+). But in these statements there is no trace of any in- 
duction that this might be a general law of chemical combina- 
tion; the opinion was not extended beyond those few cases, nor 
was it brought forward with any prominent distinction : it ac- 
cordingly attracted no attention; and Mr. Higgins himself ne- 
ver prosecuted it, nor announced it further, until he advanced 
his pretensions subsequent to the publication of Mr. Dalton’s 
System. He certainly therefore has little or no claim to. the 
doctrine.” 
_ The Doctor might add more important cases to the foregoing 
outlines; yet the few he brings forward are sufficient to’ prove, 
although he did not intend it, that the doctrine of definite pro- 
portions and the arrangement of the elementary principles of 
chemical compounds were clearly developed at that distant pe- 
riod. Why did not the Doctor give us the outlines of Mr. Dal- 
* Supposition is out of the question, all these statements are supported 
by accurate experiments. 
+ The Doctor omitted the gaseous oxide, which consists of one and one. 
Vol. 53. No. 254. June 1819. Ce ton’s 
