214 PROCEEDINGS OF THE COTTESWOLD CLUB 



has been the idea of casting, that during the last 50 years 

 the Patent OtTice has recorded almost annually the 

 attempts of some inventor, impressed with the notion 

 that he could treat the treacherous fluid successfully, or 

 in some way or another make it useful in the Arts. Few 

 people have any idea of the difficulties to be encountered. 

 The slag leaves the furnace at an excessively high tem- 

 perature, not less than 3,000*^ F. ; but when it is brought 

 into contact with anything cold, such as a mould, it readily 

 parts with its heat, and in so doing suddenly contracts. 

 The surface contracting becomes covered with fine cracks, 

 or flaws, and so much is this the case, that if allowed to 

 become entirely consolidated in the moulds, these cracks 

 will be found to penetrate completely through the casting, 

 and upon exposure to the air it falls to pieces. This is 

 the more vexing, as when slag is run into a large mass, 

 say into a pit of sand 8 or 10 feet deep, and contaming 

 from 30 to 40 tons, there is such an enormous amount of 

 heat accumulated, that it becomes self-annealing, the out- 

 side of the mass is kept at a high temperature, and if 

 allowed to remain until cool, not a flaw will be found, and 

 the slag becomes so excessively tough and hard that it 

 may be quarried like granite, and used for street paving. 



However, some extremely ingenious machinery, not 

 long since introduced, has to a certain extent got rid of 

 the difficulty, and at Tees mouth large quantities of paving 

 blocks are manufiictured direct out of the slag as it leaves 

 the furnaces. 



Mr Bashly Brittain has invented a process by which he 

 converts slag into glass, for bottle-making, and for many 

 purposes where a pure white glass is not essential. 

 Quantities of Alkali and Sand, and of colouring or de- 

 colorizing material, are added to the molten slag, varying 

 according to the quality of glass required : such as 50 per 

 cent, of slag for champagne bottles, rather less for plate 

 glass, and so on. Slag glass, owing to its toughness, is 



