ON THE METHOD OF MAKING GOLD-ASSAYS. 319 



to bo identical with that obtained from the eight sources described in the 

 above Report. 



The main constituent of oil of wormwood (termed by Gladstone Ahsintlwl, 

 and indicated by the formula Cj„Hj|.0), when treated with zinc chloride or 

 phosphorus sulphide, splits up in exactly the same way as its isomcrides 

 myristicol and camphor, water and cymene being formed, thus, 



the cymene thus formed is identical with that obtained from the other sources 

 examined. The action of phosphorus sulphide also gives rise to the produc- 

 tion of a sulphuretted compound apparently identical with the (hiocpnene, 

 C,(,IIj3 . SH, recently obtained by Flesch from the products of the action of 

 phosphorus sulphide on camphor. Further details are postponed until next 

 year's Report. 



From the circumstance that different observers have frequently obtained 

 different results in the examination of certain kinds of essential oils (e. g. the 

 different properties and compositions of myristicol and the oxidized consti- 

 tuent of citronella-oil found by Gladstone and by the writer), it would seem 

 that the composition of such oils is subject to variation, probably with the 

 age of the plant, the season, climate, &c. 



RejJort of the Committee, coyisisting of W. Chandler Roberts, Dr. 

 Mills, Dr. Boycott, and A. W. Gadesden, appointed for the pur- 

 pose of inquiring into the Method of making Gold-assays, and of 

 stating the Results thereof Drawn up by W. Chandler Roberts, 

 Secret a}-y. 



The attention of the Committee was first directed to a series of experiments 

 instituted with a view to ascertain to what extent the weights of pieces of 

 pure gold would be affected by submitting them to the process of assaying, 

 and consequently how far the results of assay operations are trustworthy. 



These results showed* that the maximum error in no case exceeded one 

 hundredth per cent, of the original weight of the assay piece, and conse- 

 quently that the results obtained by assaying gold represent the composition of 

 the portions of metal under examination to the j^jj^ part — a fact which will 

 doubtless appear remarkable to all who are accustomed to the ordinary 

 methods of quantitative analysis. 



The Committee are not unmindful that, although it is possible to attain this 

 high degree of accuracy, it is nevertheless well known that a comparison of 

 the assay repoi'ts of different assayers as to the composition of the same 

 ingot often discloses discrepancies of ^^~ parts. Thus portions of metal 

 from nineteen gold ingots were assayed by the Mint Assayerf, and were 

 then sent to five assayers, each of whom furnished an independent report. 



Two assayers alone agreed as to the value of fifteen of these ingots ; in 

 the ease of three ingots, three assayers were in accordance, while in one 

 instance all the assay reports differed ; and viewing the reports generally, 

 the discrepancies varied from ^^ to ~-^, or an average deviation of —^ 



parts. 



* Appendix I. t Appendix II. 



