6 Mr. Daniell on the Action of Mercury 



most workers in the metals, and which I have myself verified 

 by experiment. 



No metal can be hammered round upon an anvil, either hot 

 or cold. Blacksmiths very well know that they cannot forge a 

 round bar of iron ; and I have myself seen a rod of the best 

 iron which, properly heated, could be extended indefinitely, 

 when hammered square or flat, split into fibres, and become 

 perfectly disintegrated after a few blows given equally round. 

 When it is desired to give a round form to any part of a square 

 bar of iron, it is effected by forcing it, while hot, into a kind 

 of fornij or mould, of the required dimensions ; or, as is well 

 known, it may be extended in a cylindrical form to almost any 

 degree, by the equal pressure applied in the process of wire- 

 drawing. If square bars of gold, silver, or copper^ the most 

 malleable of all the metals, be hammered upon the edges, and 

 the blows repeated round, so as to give them a cylindrical 

 shape, they soon become what is technically termed rotten, and 

 break into fibres, while the bars may be extended under the 

 hammer to any degree, by blows directed parallel to their ori- 

 ginal faces, or may be beat into leaves of almost inconceivable 

 thinness, if the force be directed upon one surface only. The 

 less malleable metals, lead, brass, and tin, become even sooner 

 disintegrated when hammered round ; and, although they are 

 capable of considerable extension, when hammered square, they 

 ultimately split along the edges in a manner very similar to 

 the disintegration which I have just described as resulting from 

 the action of mercury upon the tin bar. 



It is also worthy of observation, that the metallic bars, when 

 hammered square, generally assume a rhomboidal, rather than 

 a perfectly rectangular form, and that the fissures take place 

 indifferently upon all the angles ; but if the hammering be 

 continued, they sometimes split into two, in the direction of 

 one of their diagonals, before the separation takes place in the 

 direction of the other. I have not been able to satisfy myself 

 whether this tendency to the rhomboidal form results from any 

 inequality in the blow of the hammer, producing an inclination 

 of the planes of compression to one another ; or whether it may 

 be referred to the forms of the ultimate particles of the metals ; 

 but I have ascertained that it takes place even when the greatest 



