PREFACE. HIS little book contains reprints of original memoirs TH and extracts from text-books, embracing the earliest publications by their respective authors bearing upon the foundation of the Atomic Theory. The view is pretty generally held by chemists that it was in the endeavour to explain numerous examples which were known to him, of that general regularity which is now commonly called the Law of Multiple Proportions, that Dalton was led to entertain the ideas which he held regarding the constitution of compound bodies. There has therefore been included, along with later publications, the paper by Dalton in which there is described probably the first example of this regularity with which he became acquainted. The first part of Dalton's "New System of Chemical Philosophy," containing his own account of his views, did not appear until 1808, although these views had been embodied in courses of lectures which Dalton had delivered some years previously. The earliest printed account of his views is that given by Dr Thomas Thomson in Volume 3 of the Third Edition of his "System of Chemistry," published in 1807. This account is reproduced in the following pages. A paper by Wollaston on Super-acid and Sub-acid Salts, giving various examples illustrative of the Law of Multiple Proportions, is also included. L. D. EXPERIMENTAL ENQUIRY INTO THE PROPORTION OF THE SEVERAL JOHN DALTON.* By Read Nov. 12, 1802. IN N a former paper which I submitted to this Society, "On the constitution of mixed gases," I adopted such proportions of the simple elastic fluids to constitute the atmosphere as were then current, not intending to warrant the accuracy of them all, as stated in the said paper; my principal object in that essay was, to point out the manner in which mixed elastic fluids exist together, and to insist upon what I think a very important and fundamental position in the doctrine of such fluids:namely, that the elastic or repulsive power of each particle is confined to those of its own kind; and consequently the force of such fluid, retained in a given vessel, or gravitating, is the same in a separate as in a mixed state, depending upon its proper density and temperature. This principle accords with all experience, and I have no doubt will soon be perceived and acknowledged by chemists and philosophers in general; and its application will elucidate a variety of facts, which are otherwise involved in obscurity. * From the Memoirs of the Literary and Philosophical Society of Manchester, Second Series, Volume I., 1805, pp. 244-258. In this paper there is announced the first example of the law of multiple proportions. |