Some few facts stand out quite prominently. The size of the mounds25 indicate long-continued residence—showing that these people had permanent places of abode. As they are not confined to Denmark, but are found generally throughout Europe, it would seem to imply that the Neolithic people preferred to live as fishers and hunters wherever the surroundings were such that they could by these means obtain an abundant supply of food. Some shell-heaps in Scotland were still forming at the commencement of the Bronze Age; and Mr. Geikie, on geological grounds, assigns the shell-heaps of Denmark to a late epoch of the Stone Age. It seems to us quite natural that isolated tribes, living where game was abundant, and where fishing met with a rich reward, should turn in disgust from the agricultural life of their brother tribes, and, resuming the life of mere hunters and fishers, speedily lose somewhat of their hardly won culture—for civilization is the product of labor. Whenever a people from necessity or choice abandon one form of labor for another demanding less skill to triumph over nature, a retrogression in culture is inevitable.26 Miner’s Pick. From what we have stated as to the use of flint we can readily see that it was a valuable material. Sections where it was found in abundance would as certainly become thickly populated as the iron and gold regions of our own day. In Paleolithic times the supply of flint was mostly obtained from the surface and in the gravel of rivers. In Neolithic times men had learned to mine for flint. Flint occurs in nodules in the chalk. Near Brandon, England, was discovered a series of these workings. They consist of shafts connected together by galleries. These pits vary in size from twenty to sixty feet in diameter, and in some cases were as much as thirty feet deep. From the bottom of these shafts they would excavate as far as they dared to the sides. They made no use of timbers to support the roof, and so these side excavations were not of great extent. In these old workings the miners sometimes left behind them their tools. The principal one was a pick made of deer’s horn, as is here represented. Besides these, they had chisels of bone and antler. The marks of stone hatchets on the sides of the gallery are visible.