256 MINERAL REPOSITORIES** at the depth of 150 fathoms, is 10 fathoms wide, thus gradually decreafing in width as it ap proaches its bottom. 4. Putzenwerk.—Werner. When mountains contain numerous irregular fhaped hollows, which are fometimes empty, fome- times incrufted or completely filled with mineral fubftances, fuch an appearance is denominated a putzenwerk. Thefe hollows are generally lined or filled with metalliferous fubftances, and ufually occur in limeftone. Thus the putzenwerks in the Hartz are fituated in limeftone, and are filled with ironftone; thofe in Siberia are fometimes filled with calc-finter, and fometimes with argentiferous lead-glance. We fhall conclude this geognoftic fketch by a Ihort account of the relative age of metals. CHAP. XII. RELATIVE AGE OF METALS. * t. Molybdena appears to be the oldeft of all the metals. It occurs imbedded, in fix-fided tables, in granite