design; and at the Paris Exhibition of 1867 samples of good open-hearth steel were shown by both manufacturers. In England the process is now generally known as the 'Siemens-Martin,' and on the Continent as the 'Martin-Siemens' process.
The regenerative furnace is the greatest single invention of Charles William Siemens. Owing to the large demand for steel for engineering operations, both at home and abroad, it proved exceedingly remunerative. Extensive works for the application of the process were erected at Landore, where Siemens prosecuted his experiments on the subject with unfailing ardour, and, among other things, succeeded in making a basic brick for the lining of his furnaces which withstood the intense heat fairly well.
The process in detail consists in freeing the bath of melted pig-iron from excess of carbon by adding broken lumps of pure hematite or magnetite iron ore. This causes a violent boiling, which is kept up until the metal becomes soft enough, when it is allowed to stand to let the metal clear from the slag which floats in scum upon the top. The separation of the slag and iron is facilitated by throwing in some lime from time to time. Spiegel, or specular iron, is then added; about 1 per cent. more than in the scrap process. From 20 to 24 cwt. of ore are used in a 5-ton charge, and about half the metal is reduced and turned into steel, so that the yield in ingots is from 1 to 2 per cent. more than the weight of pig and spiegel iron in the charge. The consumption of coal is rather larger than in the scrap process, and is from 14 to 15 cwt. per ton of steel. The two processes of Siemens and Martin are often combined, both scrap and ore being used in the same charge, the latter being valuable as a tempering material.
At present there are several large works engaged
