Dalton began his chemical work about six years after the death of Lavoisier. Unlike that great philosopher he cared nothing for political life. The friends in whose family he spent the greater part of his life in Manchester were never able to tell whether he was Whig or Tory. Unlike Priestley he was content to let metaphysical and theological speculation alone. In his quiet devotion to study he more resembled Black, and in his method, which was more deductive than that usually employed in chemistry, he also resembled the Edinburgh professor. Trained from his earliest days to depend on himself, nurtured in the creedless creed of the Friends, he entered on his life's work with few prejudices, if without much profound knowledge of what had been done before him. By the power of his insight into Nature and the concentration of his thought, he drew aside the curtain which hung between the seen and the unseen; and while Herschel, sweeping the heavens with his telescope and night by night bringing new worlds within the sphere of knowledge, was overpowering men's minds by new conceptions of the infinitely great, John Dalton, with like imaginative power, was examining the architecture of the ultimate particles of matter, and revealing the existence of law and order in the domain of the infinitely small. FOOTNOTES: [7] See Fig. 2, which is copied from the original in the "New System of Chemical Philosophy," and illustrates Dalton's conception of a quantity of carbonic acid gas, each atom built up of one atom of carbon and two of oxygen; of nitrous oxide gas, each atom composed of one atom of nitrogen and one of oxygen; and of hydrogen gas, constituted of single atoms. [8] More accurate analysis has shown that there are six parts of carbon united respectively with one and with two parts by weight of hydrogen in these compounds. CHAPTER IV. ESTABLISHMENT OF GENERAL PRINCIPLES OF CHEMICAL SCIENCE (_continued_)--PERIOD OF DAVY AND BERZELIUS. _Humphry Davy_, 1778-1829. _Johann Jacob Berzelius_, 1779-1848. We may roughly date the period of chemical advance during which the connections between chemistry and other branches of natural knowledge were recognized and studied, as beginning with the first year of this century, and as continuing to our own day. The elaboration of the atomic theory was busily carried on during the second and third decades of this century; to this the labour of the Swedish chemist Berzelius largely contributed. That there exist many points of close connection between chemical and electrical science was also demonstrated by the labours of the same chemist, and by the brilliant and impressive discoveries of Sir Humphry Davy. A system of classification of chemical elements and compounds was established by the same great naturalists, and many inroads were made into the domain of the chemistry of bodies of animal and vegetable origin.