402 Professor W. Chandler Boherts- Austen [March 26, 



in the facility of working, and safety belonging to a highly ductile 

 material can hardly be exaggerated." I need not point to the 

 extreme interest, in connection with my subject, of these remarks 

 from so distinguished an authority. 



The very ancient mechanical art of striking coin is wholly 

 dependent on the flow of metals. There is a popular belief that 

 the impression imparted to discs of metal during coinage, is merely 

 the result of a permanent compression of the metal of which the 

 disc is made. Striking a coin, however, presents a case of moulding 

 a plastic metal, and of the true flow of metal, under pressure, into 

 the sunk portions of the die. I once heard Mr. Euskin say : "You 

 stamp the figure of the cow on a pat of butter ; why do you not 

 impress the bee on honey ? " Simjjly because honey is not plastic 

 and is too viscous, and it flows at the ordinary atmospheric pressure. 

 This medal, struck from a series of discs, will serve to show, when 

 the discs are separated, the way the metal flows into the deepest 

 portion of the die. If the alloy used be too hard, or if the thickness 

 of the metal required to flow be insufficient, the impression will 

 always be defective, no matter how many blows may be given by 

 the press. In Mr. Browning's well-known poem, " The King and 

 the Book," there is a subtle recognition of the viscous nature of very 

 pure gold, which he characterises as " the oozing of the mine," while, 

 with regard to the manufacture of the ring, he shows : 



" Since hammer needs must widen out the round 

 And file emboss it fine with hly fiowers," 



that this is only possible because gold behaves like the honey to 

 which he comj)ares it. I have chosen this reference to Browning 

 because I happen to have a coin of " the great Twelfth Innocent," 

 the Pope of the poem I have cited, and this coin has scars on its 

 surface which prove that there was not quite enough metal to flow 

 into the depths of the die. 



If one side of a coin be ground away so as to leave a flat surface, 

 and if the disc be then struck between plain polished dies surrounded 

 by a steel collar, so as to prevent the escape of the metal, the 

 impression on the disc will be driven through the thickness of the 

 metal, and will then appear on both sides. In industrial art the 

 property of flow of metals is very important. The " spinning " of 

 articles in pewter is a familiar instance, and one which I propose to 

 illustrate. 



[A disc of pewter was spun, on a lathe, into a vase, the shadow 

 being projected on the screen during the operation.] 



The production of complicated forms, like a jelly mould, from a 

 single sheet of copper under the combined drawing and compressing 

 action of the hammer, is a still more remarkable case. 



The flow of metals is illustrated very curiously in one phase of 

 Japanese art metal work, of which, however, it is now so difficult 

 to obtain native examples, that I have been obliged to prepare, 



