Page:A biographical dictionary of eminent Scotsmen, vol 9.djvu/301

Rh tied "Försök att genom anvandandet af den electrokemiska theorien, &c.,grund-lägga för mineralogier," af J. Jacob Berzelius, Stockholm, 1814, p. 18, was sent by Berzelius to Dr. Thomson, in the same year, with a request, in a letter which is still extant, that he would endeavour to procure a translator for it. Dr. Thomson applied to Dr. Marcet and others without success; but at last prevailed on his learned friend, John Black, Esq., who so ably conducted the "Morning Chronicle" for many years, to undertake the task. Dr. Thomson graduated in 1799. He continued to lecture in Edinburgh till 1811, and during that time opened a laboratory for pupils, the first of the kind, it is believed, in Great Britain. Among those who worked in his laboratory was Dr. Henry of Manchester, a chemist, for whom he had always the greatest regard, who had visited Edinburgh for the purpose of graduation, and who there made many of his experiments on the analysis of the constituents of coal gas. During this period likewise, Dr. Thomson made his important investigations for Government on the malt and distillation questions, which laid the basis of the Scottish legislation on excise, and rendered him in after-life the arbitrator in many important revenue cases. He likewise invented his saccharometer, which is still used by the Scottish excise under the title of Allan's saccharometer. In 1807 he first introduced to the notice of the world, in the third edition of his "System," Dalton's views of the atomic theory, which had been privately communicated to him in 1804. He did not confine his remarks to mere details, but made many important new deductions, and by his clear, perspicuous, and transparent style, rendered the new theory soon universally known and appreciated. Had Richter possessed such a friend as Thomson, the atomic theory of Dalton would have long been previously fully discovered and attributed to Richter. In his papers on this theory, which occupied much of his thoughts, from the mathematical precision which it promised to impart to the science, we find numerous suggestions cautiously offered, which have often been subsequently examined and confirmed, or developed in another direction. Thus, in August, 1813, he states that, according to the atomic numbers then determined, "an atom of phosphorus is ten times as heavy as an atom of hydrogen. None of the other atoms appear to be multiples of -132 (the atom of hydrogen at that time adopted by chemists), so that, if we pitch upon hydrogen for our unit, the weight of all the atoms will be fractional quantities, except that of phosphorus alone." It was undoubtedly this observation which caused Dr. Prout to make new inquiries, and to announce, in Nov. 1815, the view that the relation of phosphorus as a multiple of hydrogen, as detected by Thomson, may be general, connecting all other atomic weights with that unit a view now generally adopted, and considered as a nearly demonstrated law.

The existence of such mathematical relations Dr. Thomson was continually in the habit of testing at the conclusion of his own researches, or in examining the experiments of others. Any peculiarity of character in a substance hitherto known, or in a newly-discovered body, he never failed to point out in his "System;" and innumerable instances have occurred, and might be mentioned did our space admit, where lucrative patents have resulted from a simple statement or foot-note, often original on the part of the author. A fact of this kind in the "Animal Chemistry" led Mr. Robert Pattison to his ingenious patent invention of lactarin, a preparation of casein from milk, for fixing ultramarine on cotton cloth; and Dr. Thomson's systematic plan of describing all the characters of bodies in detail, led Henry Rose of Berlin to the discovery of niobium