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566 and pelopium, two new metals. From the fragments of four imperfect crystals of certain tantalites, as the mineral dealers who sold them to him termed them, he was enabled to make some analyses, and to take a series of specific gravities, which he published in a paper "On the Minerals containing Columbium," in his nephew, Dr. R. D. Thomson's "Records of General Science," vol. iv., p. 407, in 1836. He found that these minerals possessed an analogous constitution, but their specific gravity differs. He termed them torreylite, columbite, tantalite, and ferrotantalite. In making his experiments he expended all the material he possessed, and he had passed the great climacteric. Professor Rose, struck with the facts, examined the minerals upon a greater scale, and, after immense labour, showed that not only columbic or tantalic acid was present in these minerals, but likewise two new acids, nlobic and pelopic acids. Instances of this kind of contribution made by Dr. Thomson to chemistry might be indefinitely particularized. About 1802 he invented the oxy-hydrogen blow-pipe, in which he introduced the oxygen and hydrogen into one vessel; but the whole apparatus having blown up and nearly proved fatal to him, he placed the gases in separate gas-holders. At that time he made many experiments on its powers of fusion, but as Dr. Hare had invented an apparatus at the same time, and published his experiments, Dr. Thomson did no more than exhibit the apparatus in his lectures. In August, 1804, in a paper on lead, he first published his new nomenclature of the oxides and acids, in which Latin and Greek numerals were made to denote the number of atoms of oxygen in an oxide. He thus introduces this important invention, which has been almost universally adopted in the science: "As colour is a very ambiguous criterion for distinguishing metallic oxides, I have been accustomed for some time to denote the oxide with a minimum of oxygen, by prefixing the Greek ordinal number to the term oxide. Thus, protoxide of lead is lead united to a minimum of oxygen; the oxide, with a maximum of oxygen, I call peroxide. Thus, brown oxide of lead is the peroxide of lead. I denominate the intermediate degrees of oxidizement by prefixing the Greek ordinals, 2nd, 3rd, 4th, &c. Thus, deutoxide is the second oxide of lead, tritoxide of cobalt the third oxide of cobalt, and so on." This paper being translated and published in France, the nomenclature was speedily introduced into that country. But the improvements which he afterwards adopted by denoting the exact number of atoms of oxygen present, by the Latin, and those of the base by the Greek numerals, and used in Great Britain, never superseded, in that country, the original suggestion in the above note.

All these inventions were merely particular parts of a systematic arrangement adopted in his "System of Chemistry"—a work which, if carefully examined with a philosophic eye, will be found to have produced beneficial results to chemical science, similar to those which the systems of Ray, Linnaeus, and Jussieu effected for botany. In his second edition, published in 1804 (the first large edition having been sold in less than ten months), he divided the consideration of chemical bodies into—Book I. Simple Substances: 1. Confinable bodies, including oxygen, simple combustibles, simple incombustibles, metals; 2. Unconfinable bodies, comprising heat and light. Book II. Compound Bodies: 1. Primary compounds; 2. Secondary compounds, &c. It is most interesting to observe how his plan was developed with the progress of the science in the different editions. It is sufficient to say that it was generally considered as a masterly arrangement, and used to be quoted