INDUSTRIES of local mines. Mr. Thomas died in 1861, leaving the works to his two sons, James and Edwin Thomas. After the death in 1880 of the former, who survived his brother, the works were carried on by the beneficiaries until 1884, when they were purchased by Mr. Martyn of St. Austell, for the purpose of starting them under a limited liability company. The present com- pany was accordingly formed, and by them the works were greatly enlarged and improved, and a bridge-building department added, with modern appliances and tools. Owing, however, to the heavy carriage expenses of sending bridges long distances this part of the business was not remunerative and was abandoned, the plant being utilized for boiler-making. A good business is done in large Lancashire and Cornish boilers for the china clay works and local mines, and for Plymouth. The works are well equipped, and are capable of dealing with the entire engineering require- ments of the mines, and more particularly of the china clay industry. Mining machinery of every description is manufactured, besides bridges, roofs, girders, tanks and other constructional iron work. Bartle's Foundry was established about the year 1860 by Messrs. Bartle, William Dunkin, Thomas Henry Tregoning and Joseph Lugg, at Cam Brea, the centre of a busy and populous district, and in the midst of mines for the purpose of supplying the latter with general foundry and iron work. By dint of hard work a good business was formed. After a few years Mr. Lugg retired, and the concern was carried on by the remaining partners until the year 1884 when, owing to disagreement, it was suspended and was offered for sale. Mr. F. Bartle, one of the founders, became the purchaser, and with his sons, Mr. Charles D. Bartle and Mr. William Bartle, who returned from America for the purpose, has carried on the business ever since under the title of F. Bartle & Sons. The works have been enlarged, and the business considerably developed, being well known in the mining world. The persons employed number from 70 to 100. The manufactures include the Murdoch Rock Drill and tube mills. The patent of the latter was held by this firm, and was formerly known as the Barrel Pulverizer. Michell and Tregon- ing's Pulverizers are also made ; large numbers of both kinds are working in Cornwall and other places. The firm also make a speciality of slime-dressing machinery, and have just patented an improved Slime Concentrator. They are also well-known makers of double faggoted iron, large quantities of which they send to South Africa. CHINA CLAY No account of Cornish Industries can claim to be complete which does not include a sketch, however brief, of that industry which is, and has always been, since its inception about the middle of the eighteenth century, the most uniformly progressive of them all. The causes, mechanical and chemical, which have led to the formation of china clay are well known. On the one hand, variations of tempera- ture and the congelation and consequent expansion of water within the minute pores of granite rock ; on the other,the concurrent chemical action of car- bonic acid, robbing the felspar and mica contained in the granite of their potash ; these are com- monly held to have been the chief causes of that process of disintegration by which china clay, or kaolin, has been formed. 1 Wherever in Cornwall there is a granite formation the Carnmenellis district excepted china clay has been formed. West Penwith, Breage, the moors north of Bodmin, all contain deposits ; but by far the most considerable as well as the most valuable clay beds are those of the Hensbarrow district which embraces large portions of the parishes of St. Austell, St. Blazey, 1 It should be mentioned that a very competent writer, Robert Hunt, F.R.S., considers china clay to be granite which has never properly been formed, rather than granite which has undergone decomposition, See British Mining, p. 196. Luxulian, Roche, St. Denys, St. Enoder and St. Stephen in Brannel. About the middle of the eighteenth century the presence of this valuable product became known to the potter. Mr. William Cookworthy, who had established a pottery in Plymouth in 1733, obtained in conjunction with Lord Camelford a patent for the use of china clay in 1768. In 1813 there were seven clay beds being worked in the Hensbarrow district, the largest of which produced about 300 tons of clay per annum. 2 The amount of china stone shipped at Charlestown in 1816-17 was 2 > Z 35 tons > and of china clay 1,775 tons. 3 Since that time the returns have steadily increased, as will be seen from the following table 4 : Year. China Clay. China Stone. Total. 1816 . 1,775 . 2,135 . 3,910" 1826 . 7,538 . 5,252 . 12,790 3 1838 . 13,440 . 7,344 . 20,784 3 1855 . 60,188 . 19,961 . 80,149* 1864 . 95,73 21,570 . 117,300* 1874 . 150,500 . 42,500 . 193,000* 1894 . . . 386,648* 1903 . 490,881 . 53,680 . 544,561* i94 5i5,45i 66,994 . 582,445* 2 Annals of Philosophy, vol. ii, p. 475. 3 Trans, of the Geol. Soc. ofCornio. 4 Mineral Statistics, published by the Home Department. 577 73
