Plate XXVIII. AAAA, fig. 1. is a front elevation of an assay furnace; aa, a view of one of the two iron
rollers on which the furnace rests, and by means of which it is moved forward or backward; b the ash-pit, c c are the ash-pit dampers, which are moved in a horizontal direction towards each other for regulating the draught of the furnace; d the door or opening by which the cupels and assays are introduced into the muffle; e a moveable funnel or chimney by which the draught of the furnace is increased.