MISCELLANEOUS. 337 



To make very beautiful Artificial Petrifactions. 



Put into a retort a quantity of pounded fluor 

 spar and a few bits of broken glass, and pour upon 

 them some sulphuric acid ; fluoric acid gas will 

 be disengaged, holding silex in solution. The 

 substances to be made to resemble petrifactions, 

 as lizards, frogs, branches of trees, birds nests, &c. 

 must now be moistened with water, and placed 

 in a vessel connected with the neck of the retort. 

 The fluoric acid gas will be absorbed by the 

 moisture adhering to the substances, and the silex 

 will be precipitated upon them like a sort of hoar- 

 frost, which will have a very beautiful appearance, 

 and is very durable. 



A Method of making Cast Steel. 



This method has been invented in France. 

 It is as follows : Take small pieces of iron, and 

 place them in a crucible, with a mixture of chalk 

 or lime-stone and the earth of Hessian crucibles. 

 Six parts of chalk and six of this earth must be 

 employed for twenty parts of the iron. The mat- 

 ters are to be so disposed, that, after fusion, the 

 iron must be completely covered by them, to pre- 

 vent it from coming into contact with the external 

 air. The mixture is then to be gradually heated, 

 and at last exposed to a heat capable of melting iron. 

 If the fire be well kept up, an hour will generally 

 be sufficient to convert two pounds of iron into 

 excellent and exceedingly hard steel, capable of 

 being forged ; an advantage not possessed by steel 

 made in the usual manner. 



VOL. II. z 



