In England the valleys of the Thames and other rivers were heavily wooded and not populated until much later. But the long lines of chalk-downs and oolitic uplands were far less favorable to forest growth. In Norfolk and Suffolk there were apparently open spaces. Yorkshire and Derbyshire had very similar landscapes. The forest was held back wherever the porous chalk formation made a large outcrop. In these places man could settle and find pasturage for his flocks and attempt a poor sort of agriculture, even in Neolithic days. Hence we find these regions dotted with Neolithic settlements. The immigrants who came in during the Bronze period settled in the same regions. Here again clearing of the forest on any large scale was apparently not attempted until Roman times, but along its boundaries, where the forest growth was not too heavy, these primitive agriculturists may well have cut off the lighter growth for fuel and buildings, and thus have gradually appreciably extended the arable area. CHAPTER IV LAKE-DWELLINGS The winter of 1853-1854 was exceedingly cold and dry. The surface of the Swiss lakes sank lower than at any time during many preceding centuries. The lowering of the water tempted the inhabitants along the shore to erect dikes and thus fill in the newly gained flats. During this process the workmen along the edge of the retreating water came upon the tops of piles, and between those great quantities of horn and stone implements and fragments of pottery. Aeppli, a teacher in Obermeilen, called the attention of the Antiquarian Society in Zurich to these discoveries. The society recognized at once their importance, and under the leadership of its president, Ferdinand Keller, began a series of most careful investigations which have contributed more to our knowledge of life during the Neolithic period than any discoveries before or since. The number of these lake-dwellings is very large. Lake Neuchatel has furnished over 50; Lake Leman (Geneva) 40; Lake Constance over 40; Lake Zurich 10. The shores of the smaller lakes have also contributed their full quota.[49] In some of the lakes where the shore was favorable, remains of a lake-dwelling have been found before almost every modern village. Sometimes we find the remains of two villages, one somewhat farther out than the other. In these cases the one nearer the shore is the older, usually Neolithic, while the one farther out belongs to the Bronze period.