Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/822

Rh 78(5 D A L T N is his belief that the forces of atoms measure the attraction of matter, yet he ventures on no deduction as to the com parative numbers of the attracting atoms. Upon these views we find an advance in the writings of William Higgins, who not only held that atoms combined to form molecules of compound bodies, but reasoned that they must unite singly or by twos and threes, there being no inter mediate division of atoms ; nowhere, however, does he attempt to elevate his conclusions into a general law. Next Richter, and after him Fischer, showed the existence of definite quantitative relations between the constituents of bodies, but for these relations they assigned no cause ; and it was reserved for Dalton to give to the world a theory which linked together and reduced to order and simplicity the previously disconnected and unexplained phenomena of chemical combination. Till 1811 Dalton, who drew his deductions from his own rough experimental work, was un acquainted with the observations of William Higgins ; and although Richter s determinations may have aided him in the proving of his laws, still, as Dr R. A. Smith has remarked, &quot; they could never have given him fundamental ideas.&quot; Dalton makes the following clear distinction between his own researches with respect to the ultimate constitution of matter and those of other chemists (New System, pt. i. p. 213, 1808) : &quot; In all chemical investigations, it has justly been considered an important object to ascertain the relative weights of the simples which constitute a compound. But unfortunately the inquiry has terminated here ; whereas from the relative weights in the mass, the relative weights of the ultimate particles or atoms of the bodies might have been inferred, from which their number and weight in various other compounds would appear, in order to assist and to guide future investigations, and to correct their results. Now, it is one great object of this work to show the importance and advantage of ascertaining the relative weights of the ultimate particles, both of simple and compound bodies, the number of simple elementary par ticles ichich constitute one compound particle, and the number of less compound particles which enter into the formation of one more compound particle. If there are two bodies, A and B, which are disposed to com bine, the following is the order in which the combinations may take place, beginning with the most simple, namely : 1 atom of A + 1 atom of B = 1 atom of C binary. 1 atom of A + 2 atoms of B = l atom of D ternarv. 2 atoms of A + 1 atom of B = 1 atom of E ternary. 1 atom of A + 3 atoms of B = 1 atom of F quaternary. 3 atoms of A + 1 atom of B = 1 atom of G quaternary, &c. , &c. &quot; In 1810 appeared the second part of volume i. of the New System, in which the chemical elements are described. The first part of volume ii. was not published till 1827 j it by no means represents the advanced state of chemical science at that time, and the appendix, giving Dalton s latest views, is the only portion of it that is of any special interest. A history of the development of the atomic theory since its first promulgation will be found under CHEMISTRY, vol. v. p. 465. By Dr Thomson, its first advo cate, by Wollaston, and by Dr Henry, it was ably supported, and the analyses of Berzelius placed it on a stable footing. &quot; The theory of multiple proportions,&quot; wrote Berzelius, &quot; is a mystery without the atomic hypothesis.&quot; Strange to say, the conclusions of Gay-Lussac with regard to the combiuing volumes of gases, which afforded the strongest evidence in favour of the atomic theory, were distrusted, and perhaps never fully accepted by Dalton. The tenacity with which he clung to opinions once formed is further exemplified by his unwillingness to recognize chlorine as a chemical element, and his persistent use of the atomic weights first adopted by him, in spite of the later and more trustworthy deter minations of other chemists. The memoirs of Dalton read before the Manchester Literary and Philosophical Society were in all 110. In one of these, read in 1814, he lays down the principles of the volumetric method of analysis, of which he is undoubtedly to be regarded as the originator, although its wide practical application is the result of the labours of numerous after-chemists. The earlier of Dalton s papers are the most important and complete ; one of his latest, however, &quot; On a New and Easy Method of Analyzing J3ugar,&quot; describes a discovery of much interest, viz., that the volumes of highly hydrated salts when dissolved are equal to those of their volumes of water, the volume of the salt itself disappearing. Before Dalton had become known as the propounder of the atomic theory, he had already attained a considerable reputation by his scientific labours, and in 1804 he was chosen to give a course of lectures on natural philosophy at the Royal Institution in London. Subsequent discourses were delivered by him at the same place in the winter of 1809-10. He was, it would seem, deficient in many of those qualities that go to form an attractive public lecturer. His voice is said to have been harsh, indistinct, and unemphatic, and his manner of dealing with his subject ineffective ; he is described, more over, as an indifferent experimenter, and as &quot;singularly wanting in the language and power of illustration.&quot; An imaginative or brilliant style of diction, it is to be supposed, can scarcely have been at the command of one whose hours of leisure from the routine of tuition were unceasingly devoted to laboratory work, and who eschewed, and even to some extent discouraged, literary pursuits. His library, he was once heard to declare, he could carry on his back, and yet he had not read half the books which constituted it. In the autumn of 1805 Dalton went to live in George Street, Manchester, with his friend the Rev. W. Johns, and with him and his family he continued to reside, in the greatest harmony, for the next twenty-six years. Engaged in his favourite studies, he passed a quiet and almost uneventful life, interrupted only by occasional visits to London and other cities, and by annual excursions to the Lake country. Into society he rarely went, and amusement he had none, with the exception of a game at bowls on Thursday afternoons. In 1810 he was asked by Davy to offer himself as a candidate for the fellowship of the Royal Society, but he declined, possibly from pecuniary considera tions. In 1822 he was proposed without his knowledge, was elected, and paid the usual fee. Four years later he received the king s medal of the society, &quot; for the development of the chemical theory of Definite Proportions usually called the Atomic Theory, and for his labours and discoveries in physical and chemical science.&quot; In the summer of 1822, in company with Mr Benjamin Dockray and Mr W. D. Crewdson, Dalton spent a short time at Paris, where he met Ampere, Arago, Berthollet, Biot, Brequet, Cuvier, Fourier, Gay-Lussac, Laplace, Thenard, Vauquelin, and other distinguished men of science. Six years previously he had besn made a corresponding member of the Academy of Sciences; and in 1830 he was elected by that body to fill the place of Davy as one of its eight foreign associates. Dalton was present at the first meeting of the British Association, held at York in 1831. On the occasion of the second meeting, at Oxford in 1832, the honorary degree of D.C.L. was conferred upon him. The scarlet hue of his doctor s gown was to him, he said, &quot; that of nature,&quot; the colour of &quot; green leaves.&quot; In June 1833, Lord Grey s Government conferred upon Dalton an annual pension of 150, which in 1836 was raised to &amp;lt;300. In the former year a subscription list was opened in Manchester to obtain funds for providing that city with a lasting memorial of its great chemist; and the sum of 2000 having been raised, Chantrey was intrusted with the execution of a bust, which was eventually placed in the entrance hall of the Manchester Royal Institution. During his stay in London, whither he had gone in 1834 to sit to the sculptor, Dalton was presented at court, and in the autumn he received from the university of Edinburgh