560 Chronicles of Science. [Oct., 



with earth when the pit is filled. When cold the mass is found to 

 leave a widely-radiated structure, recalling that of natural volcanic 

 rocks, and the texture is that of a finely crystalline or granular 

 porphyry, having a mean specific gravity of 2 ■ 77. The surface is 

 said to wear in such a manner as not to become slippery under 

 traffic, and the cost to he 20 per cent, less than that of ordinary 

 stone paving. It is very much to be desired that experiments of 

 this character should be carried out in the only district in this 

 country where blast-furnace slags are used as a road material to 

 any great extent, viz. in Northamptonshire, where, according 

 to the present method, the general character of the roads may be 

 represented by a series of parallel ruts filled with broken glass, 

 owing to the slag used being cooled in small masses, producing a 

 vitreous substance unfitted for road making, but which is used 

 owing to the difficulty of obtaining natural stone for the purpose. 



A new process of casting metals has lately been attracting con- 

 siderable attention. In July a number of gentlemen met at the 

 Lancashire Engineering and Compression Casting Works, at St. 

 Helens Junction, to witness the new process of casting in brass 

 and iron chased and embossed work of the most elaborate descrip- 

 tion. The process, which was here for the first time exhibited in 

 England, is an American invention, and its utility was shown to 

 consist in this — that any design, whether in high or low relief, 

 chased on metal of any required pattern or shape, whether flat as a 

 door-plate or round as a vase, can be produced by castings from it 

 ad infinitum, and each casting will show upon it all the sharpness 

 and beauty of the original chasing. Moulds are made with a pre- 

 paration of fine clay from the articles to be reproduced. The 

 making of one of these moulds takes a person from five to ten 

 minutes. The moulds have then to stand twenty-four hours ex- 

 posed to dry air, after which they are baked in a furnace for eight 

 hours. These clay moulds, into which the metal is afterwards 

 poured, are, to all intents and purposes, encaustic tiles. The 

 moulds are placed in a box, and the air is extracted from them so 

 as to form a vacuum, after which the molten metal is forced into 

 them, and in this way, in ten minutes, a casting can be completed. 

 When the casting is taken out, the design, however intricate, is 

 found to be perfectly represented, with the exception of removing a 

 slight surface of clay from it, which can be done in half an hour, 

 and the article is then ready to be sent to the bronzer, instead of 

 having to be kept in the chaser's hands. In this way an enormous 

 amount of cost and labour on ornamental articles in metal is saved. 



A new process for refining and desilvering lead has been intro- 

 duced by Gustave Luce, Son, and Bozan, of Marseilles. The 

 invention consists in the application of steam. For this purpose 

 the crude argentiferous lead is melted down in a vessel heated by a 



