300 



Y. KOGA & 0. YAMAGATA. 



a miniature catting machine similar in construction to that used in 

 minting operations being provided for the purpose. The discs are 

 then well mixed and a number of them is weighed into a single assay. 

 This method involves a considerable amount of labour in roll in £f and 

 cutting, especially when a large number of coins is to be daily assay- 

 ed. It may perhaps be difficult to guard the small and thin discs 

 belonging to a particular coin against contamination with very minute 

 scraps of silver detached from another coin operated in the same 

 machine. Besides we are inclined to think that a number of such 

 discs, unless indeed they be very minute, taken together for an assay 

 does not always represent the average sample of the whole coin. 

 Some experiments made by us in this connection show that the 

 results of many assays made on a single coin are not sufficiently 

 concordant. 



Method c. A method formerly employed in the Imperial Mint 

 consists in cutting four equal isosceles triangles from diagonal posi- 

 tions as shown in Fig. 6., the sharp angles of the triangles meeting 

 at the centre of the coin, and the four portions when put together 

 weighing almost exactly the weight required for an assay. 



Fig. 6. 



As may be understood from the nature of segregation already ex- 

 plained, this method does not provide the true representative sample 



