The remarkable differences in the mode of interment, which have been only sketchily described on the foregoing pages, present a highly interesting problem to be solved. The prevailing view is that these different modes were practised simultaneously by different tribes, and even by the same people. The double interments, in which an unburnt skeleton is associated with a deposit of cremated remains, may seem to countenance the latter view, while the distribution of the interments favours the former. For instance, in certain districts certain modes prevailed. On and around Stanton Moor, and throughout the country between Eyam, Castleton, and Sheffield, cremated interments predominate, while in many parts of the west of the county the interments are exclusively unburnt. Then, again, in barrows containing many burials there is a decided partiality for like rather than unlike interments. But if the phenomena are subjected to a careful and systematic study, it will be found that these differences are neither local nor tribal, but in the main consecutive. The problem is solved by the superposition and other evidences of sequence of the different interments in those barrows which contain several, with the comparison of the associated objects, and then by a general correlation of the results derived from the individual barrows. It is by a similar process that the geologist establishes the sequence of his formations; the fossils playing the part of the associated objects. The pottery is a peculiarly valuable factor in the enquiry, as in spite of the conservatism of half-civilised people, the ease with which the plastic clay can be modelled into any desired shape resulted in comparatively rapid changes in form and decoration. In this respect the pottery contrasted with the flint and stone implements, the intractability of the materials of which limited the workman to a narrow range of forms; hence these forms continued unchanged through long periods. We will now give a few illustrations. [Illustration: Fig. 12.—Typical Examples of Bronze Age Burial Vessels, Derbyshire. A—Incense-Cups. B—Cinerary Urns. (Scale = 1/5 size of originals.) ]