Om the Atomic Theory. 165 



plain the cause of definite projjortions ; and we want not greater 

 proof of this than the fact of the true cause not being known till 

 twenty-eight years after Mr. Higgins had told us that one par- 

 ticle of sulphur and one of oxvgen formed sulphurous acid, and 

 that one to two formed sulphuric acid. These loose expressions 

 were but a small step indeed towards the discovery of the Atomic 

 Theory in its present form, which has placed chemistry on the 

 same ground with that on which the discovery of the laws of 

 gravity placed the science of astronomy." 



The above paragraph is written with a great deal of disin- 

 genuity, and evidently could only flow from the pen of a pre- 

 judiced man. We could never be acquainted with the cause of 

 definite proportion without first knowing that compounds con- 

 sisted of elementary particles ; and the proportions of those par- 

 ticles, the relative forces with which they unite in different com- 

 pounds, and their relative weights : — all these constitute the 

 Atomic Theory ; and those important circumstances are unequi- 

 vocally, not loosely, to be met with in my Comparative View. 

 It was the pride of my life since 1 had written that work, to feel 

 that " I placed chemistry on the same ground with that on 

 which the discovery of the laws of attraction placed the science 

 of astronomy." 



The following quotation from the preface of my Essay on 

 Bleaching, page 18, will show how confident I was that what 

 I advanced in my Comparative View was perfectly ji'.st, viz. 

 *^ I have connected the whole (the facts and phsenoniena then 

 known) and reduced them to a system, and made use of demon- 

 strations, which in my opinion are not to be invalidated or con- 

 tradicted, until the order of natural things assume a different 

 aspect." 



The above Essay was published in the year 1799, many years 

 before Dalton's work appeared. — But to return to our writer. 



" We are inclined to believe that the first step towards this 

 important discovery was given by Richter. He found in the 

 double decomposition of salts, that the acid of one salt was al- 

 ways just sufficient to saturate the base of the other, and vice 

 versa." So far as the decomposition takes place this holds good, 

 but in other respects there are many exceptions. 



" He also ascertained, that when one metal was precipitated 

 by another, the oxygen of the precipitated metal was just what 

 was required by the precipitating metal." 



I wrote several years before Richter; and many of the chemists 

 of the time at which I published, as well as myself, were acquainted 

 with what this gentleman attributes to Richter*. The ancients 



• The mutual saturation of saline bodies on interchanging acids and 

 bases with each other ; that is, double decomposition. 



L 3 kn-jw 



