1899 an amalgamation, and important steel works were built at Clarence. The Clarence works are now producing about 1000 tons of pig iron daily, and 4000 tons of ingots and 2400 tons of finished steel weekly.
Yet another industry was added later to the wide range of the firm's activities. The discovery (during boring operations for water) of rock salt at a depth of 1200 feet below the surface on the south side of the river Tees by Messrs. Bolckow & Vaughan in 1862 induced Messrs. Bell Bros., in 1874, to sink a bore-hole near their Clarence works. The result was that salt was encountered at a depth of 1127 feet below the surface; the salt bed at this point being about eighty feet thick and estimated to contain about 200,000 tons to the acre. It was not, however, until 1881, when Thomas Bell suggested (after independent thought) the adoption of a special mode of winning the salt, which (as he subsequently found) had been long practised near Nancy, that the firm proceeded to realise this new asset. Two years later they were making 320 tons of salt per week.
The firm of Bell Brothers in all its branches became in Lowthian Bell's lifetime a gigantic concern employing in its mines, collieries, and ironworks some 6000 work-people. Bell was always active in numerous directions beyond the immediate and varied calls of business. He constantly travelled abroad, and closely studied the conditions of iron manufacture in foreign countries, especially in America. His work in applied science almost excelled in importance his labours as an industrial pioneer. In both capacities his eminence was soon universally acknowledged. Taking an active part in the establishment of the Iron and Steel Institute in 1869, he filled the office of president during 1873–5, and was the first recipient of the Bessemer gold medal in 1874. He helped to found in 1888 the Institution of Mining Engineers, of which he was president in 1904. He was also president of the Institution of Mechanical Engineers (1884), of the British Iron Trade Association in 1886 and of the Society of Chemical Industry (1889). In 1895 he was awarded the Albert medal of the Society of Arts, and in 1900 the George Stephenson medal from the Institution of Civil Engineers, as well as a Telford premium for a paper on rails in Great Britain.
Bell's scientific attainments rank very high. 'For the last fifty years of his life he had few superiors in general knowledge of chemical metallurgy and he was an unrivalled authority on the blast furnace and the scientific processes of its operation' cf. Roy. Soc. Proc. 1907, p. xvii). Between 1869 and 1894 he embodied in papers in the Iron and Steel Institute's 'Journal' the results of exhaustive experimental researches. Among the most important were: 'The Development of Heat and its Appropriation in Blast Furnaces of Different Dimensions' (1869); 'Chemical Phenomena of Iron Smelting' (1871 and 1872); 'The Sum of Heat utilised in smelting Cleveland Ironstone' (1875); 'The Separation of Carbon, Silicon, Sulphur, and Phosphorus, in the Refining and Puddling Furnace, and in the Bessemer Converter' (1877); 'The Separation of Phosphorus from Pig Iron' (1878); and 'On the Value of Excessive Addition to the Temperature of the Air used in Smelting Iron' (1883).
The outcome of Bell's experimental researches upon blast furnace practice, in which he was assisted by Dr. C. R. A. Wright, was published in 1872 in his classical 'Chemical Phenomena of Iron Smelting; an experimental and practical examination of the circumstances which determine the capacity of the blast furnace, the temperature of the air and the proper condition of the materials to be operated upon' (translated into French, German and Swedish). In his research on the blast furnace he had taken full advantage of contemporary research and invention and advanced beyond them. He explained the economy of hot blast which James Beaumont Neilson [q. v.] demonstrated in 1828, and indicated the limits beyond which it could not be pushed in practice; Bunsen and Playfair, by the analysis of the gases at various levels of the furnace, had proved the main source of avoidable loss in current blast practice, and had elucidated the chemistry of the process; Bell amplified and completed their work both by establishing a true basis for estimating the 'heat balance' of the furnace, and by determining once and for all the main sequence of the chemical changes as the descending charge of ore, fuel, and flux met the ascending furnace gases; finally he supplemented the inventions of regenerative stoves made during 1860–5 by Edward Alfred Cowper (d. 1895) and Thomas Whitwell, which rendered high blast temperatures possible and led to the construction of much larger furnaces; Bell demonstrated on scientific grounds how far the furnace dimension could be increased in the interest of fuel economy, apart from any purely mechanical difficulties. In his book he fully expounded the various
