[ *3 ] 68. There are fometimes found native fulphurs, which are tranfparent like yellow amber, anti have fine bright colours; others, in the form of ores, are very gloffy, and of regular angu- lated figures, and have a glofs like a real bur- niffied metal; but they foon betray their ful- „ phureous particles, by the fuffocating fumes they yield, when put on a red-hot fhovel. SECTION VI. » On Metallic Subjlances. 69.. IN regard to metallic fubftances, it mult be obferved, that when they are pure and upmixed, it is not a very difficult matter to K find the quality of the metal; but in cafe they are mixed, and the nobler metals, for inftance, have fome alloy of the bafer ones •, ^ or if the metallic fubftances are in the vari ous ores mixed with fulphureous, arfenical, and other particles, it is impoffible to give inftruftions for finding their contents, with out giving a full detail of the whole art of Aflaying ; which would go beyond our in tended plan. We therefore content our- felves with giving fuch inftruiftions as will enable every man, with moderate parts, and with no other apparatus than that which we recommended at the beginning of our paper, ’• to afcertain the metal contained in an ore. 70. We fuppofe the experiments will be made with fmall portions of the ores or metals; fo that, if at all, any wafte of them fhould be made, the lofs may not be great. I< X P F.-