1870.] On the Method of Assaying Silver. 389 



figures representing the proportion per mille of pure metal which 

 such a weight of chloride so found corresponds to ; thus, supposing 

 a melting of five franc pieces was being assayed, and the chloride 

 resulting from the assay pound operated on, weighed 22.5 grains, 

 (shewing the actual pure contents in the sample to be 16.94 grs.), 

 instead of referring to a table to see the equivalent per mille-age 

 of pure silver, that weight which is actually 22.5 grs. has 900 

 marked on it, and the assayer simply reads the touch from it. 

 Accordingly the assay weights are as follows : — 



Actual Weight, Figures marked on 



in grains. the weights. 



25 , 1000 



22-91 (Std.) 916-66 



22-5 900 



20 800 



17-5 700 



15 600 



12-5 . 500 



10 , 400 



7-5 300 



5-0 200 



2-5 100 



1-25 50 



1-0 40 



0-75 30 



0-50 , 20 



0-25 10 



0*125 oBCseat 5 



0100 4 



0-075 3 



0-050 2 



0-025 1 



Assay ft>., weight = 18-825 grains. 



The assays for the valuation of merchants' bullion are reported 

 to the Yo^th part, i. e.> the value of our smallest weight, and as 

 the distance from zero to the point (shown by a scale and indica- 

 tor) at which the balance " breaks" with this weight in either 



