of Dies for Medals and Coinage. 119 



coats of an onion ; an arrangement which wc sometimes have 

 an op[)ortunity of seeing displayed in dies which have been 

 smashed by a violent blow. 



The hardening having been effected, and the die being for 

 the time safe, some further steps may be taken for its protection ; 

 one of these consists in a very mild kind of tempering, con- 

 sisting in putting it into water gradually raised to the boiling 

 point, till heated throughout, and then suffering it gradually to 

 cool. This operation renders the die less apt to crack in very 

 cold weather. A great safeguard is also obtained by thrusting 

 the cold die into a red-hot iron ring, which just fits it in that 

 state, and which, by contracting as it cools, keeps its parts 

 together under considerable pressure, preventing the spreading 

 of external cracks and fissures, and often enabling us to employ 

 a split die for obtaining punches, which would break to pieces 

 without the protecting ring. 



If the die has been successfully hardened, and the protecting 

 paste has done its duty, by preserving the face from all injury 

 and oxydizement, or burning, as it is usually called, it is now to 

 be cleaned and polished, and in this state constitutes what is 

 technically termed a matrix : it may of course be used as a 

 source of medals, coins, or impressions, but it is not usually 

 thus employed, for fear of accidents happening to it in the 

 coining press, and because the artist has seldom perfected his 

 work upon it in this state. It is, therefore, resorted to for the 

 purpose of furnishing a punch, or a steel impression in relief. 

 For this purpose a proper block of steel is selected, of the 

 same quality, and with the same precautions as before, and 

 being carefully annealed, or softened, is turned like the matrix, 

 perfectly true and flat at the bottom, and obtusely conical at 

 top. In this state, its conical surface is carefully compressed 

 by powerful and proper machinery upon the matrix, which 

 being very hard, soon allows it to receive the commencement 

 of an impression ; but in thus receiving the impression, 

 it becomes itself so hard by condensation of texture, as to 

 require during the operation to be repeatedly annealed, or 

 softened, othenvise it would split into small superficial fissures, 

 or would injure the matrix. Much practical skill is therefore 

 required in taking this impression, and the punch, at each 



