s 571 ]

a third time. The first cupels were tinged of a deeprusty colour, probably from the irony matter in the pla-tina; the others only yellowish, as from lead alone. Theplates of metal, after the first cupellation, were dull co-loured and stuck to the cupels; after the others, they werebrighter and did not stick. The four plates, weighing3031 grains, kept for twelve hours on a scorifying disli, inas strong a fire as could be excited in the assay furnace, be-came whiter, and lost 218 grains: the white dish was co-vered all over with a yellow glazing. The plates, whichhad suffered no appearance of fusion, and which still provedbrittle though much less so than before, were broken intosmaller pieces, and set on four cupels, under a muffle, inthe wind-furnace above described: during eight hours ve-hement fire, the two cupels in the fore part of the muffle,which was less hot than the back part, were observed, asoften as the door was kept open for a little while, to smokeconsiderably; but all the air that could pass into the muffle,did not so far diminish the dazzling heat, as that anyfumes could be distinguished in the back part. The archand further end of the muffle were found all over glazedby the fumes; the cupels friable and unstained; the metalof a silver whiteness, and diminished 105 grains. Thepieces in the front cupels were still brittle; those in thefurther ones bore to be fattened considerably under thehammer, and seemed nearly as soft as alloyed silver.

18. I made many other cupellations of the same kind;of which, as no other remarkable phenomena occurredthan have been already mentioned, it would be unnecessaryto give a particular detail. They agree in establishingan important fact, that though in the common pro-cess of cupellation, even when performed with strongersires than the cupelling furnace can give, and continuedsome hours beyond the time in which the fixing of the

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