124 



Mr. E. Matthey. 



[Jan. 11, 



" Constant-Standard Silver Trial-Plates." By Edward Matthey, 

 C.B., F.S.A., F.C.S., Assoc. Boy. Sch. Mines. Communicated 

 by Sir William Crookes, E.B.S. Beceived January 11, — 

 Bead February 11, 1904 



Beferring to my paper communicated to the Boyal Society, 

 February 16, 1894, and read March 15, 1894,* in which it was shown 

 that moderately sized plates of sterling silver of a uniform standard 

 could be obtained by casting from thin castings, my attention since 

 then was drawn to the difficulty of casting larger quantities than those 

 described in that paper, which were only of an average weight of 

 4 to 5 kilogrammes per plate, and to the desirability of obtaining a 

 large plate, say of some 8 or 10 kilogrammes in weight, without 

 difficulty, and I have therefore resumed my ''attention towards 

 effecting this. It appears that considerable difficulties have been 

 experienced with regard to obtaining large plates of constant standard. 



In the Boyal Mint Beport of 1873 is a memorandum appended by 

 Professor W. Chandler Boberts, which refers to a series of well-known 

 experiments with regard to obtaining a constant alloy of • 900 silver 

 by Levol in the Paris Mint, he himself being at the time engaged in 

 the preparation of a standard silver trial-plate. Professor Chandler 

 Boberts states : — "From the foregoing remarks it will be evident that 

 it is impossible to cast a standard silver plate or bar of uniform composition, 

 and it was necessary therefore to resort to an artifice in order to 

 obtain a standard trial-plate of the required dimensions."! 



The means adopted by him were to cast 1000 ozs. of standard silver 

 into a skillet-mould 30 cm. long, 25 cm. wide and 5 cm. broad, to 

 plane off 4 mm. from its surface and to roll the planed skillet to 

 1"8 mm. thickness, a sheet being produced 1*5 m. long, 45 cm. wide. 

 From this the portion was cut which showed constant results about 

 925, but which varied from 924 • 6 — 925 ■ 1 ; and the rest of the plate 

 which varied from 924 (lowest) to 928*4 (highest) was abandoned. 

 He shows all these results by diagrams accompanying his memoranda. 

 The portion of available constant standard so cut out from the 

 1000 oz. sheet weighed 104 oz., about one-tenth of the whole plate. 

 And this 104 oz. ( = 3 '230 kilogrammes) formed the mint trial plate 

 from a mass of 1000 oz. (= 31*103 kilogrammes) specially cast for 

 the purpose. 



Notwithstanding that many experiments were subsequently made 

 by Professor Boberts Austen to find a means of obtaining a constant 

 standard trial-plate, in 1899 he was compelled to resort to what he 

 calls the " cumbrous expedient " of 1873. His statement is : — " None 



* ' Roy. Soc. Proc, 5 vol. 55, 1894, p. 265. 



f Fourth Annual Keport, Deputy Master of Mint, 1873, pp. 44 — 46. 



