GEOLOGY AND HISTORY. 499 



coast, backed by a forest-belt on the oolite in the rear, may have checked 

 his westward advance through the fear of meeting the cave-lions and 

 other savage wild beasts of the preglacial period on the open plain. 



At a far later date, when man had progressed from the hunting to 

 the pastoral stage, and had learned to fashion weapons of polished 

 stone or bronze, which made him the acknowledged master of the brute 

 creation, it is clear that a great change must have taken place as re- 

 gards the relation to geological conditions. And in Britain the men 

 of this later period certainly spread over the whole country, gathering 

 most thickly, it would seem, where pasturage was easiest for their 

 herds and flocks. This would naturally be upon those same undulating 

 chalk downs which were doubtless objects of terror to the earlier race. 

 Hence we find the tumuli and other memorials of the Euskarian and 

 Keltic inhabitants belonging either to the neolithic, the bronze, or 

 the iron age most thickly clustered around the great monument of 

 Stonehenge on Salisbury Plain, among the downs about Brighton or 

 Lewes, and on the sides or summits of the Yorkshire and Lincolnshire 

 wolds. In those days and for many centuries after, the Weald of 

 Kent lay as a wild forest-belt between the open chalk country to the 

 north and south ; while the primary hills and the river valleys still 

 consisted for the most part of unbroken underbrush and woodland. 

 Even in these early times, however, a commerce based upon geological 

 differences had already sprung up : for the beautiful jade, employed 

 as material for the finest hatchets, has been recognized as coming from 

 the Kuen-Lun Mountains of Central Asia, while amber was already 

 imported from the banks of the Baltic. Within Britain itself the Corn- 

 ish tin-mines probably supplied the metal which mingled with copper 

 to form the bronze implements of all Western Europe. An industrial 

 population must even then have gathered with comparatively consid- 

 erable density above the ores of the Land's End, while the valley of 

 the Thames remained a mere desolate jungle wandered over by a few 

 stray families of savage hunters. 



Agriculture must first have developed itself over the whole world 

 on low alluvial ground. Hence we find that all the great early civili- 

 zations occupy river valleys such as those of the Nile, the Euphrates, 

 the Ganges, the Indus, and the Hoang-Ho. Here alone can large 

 masses of men obtain subsistence, before navigation and scientific 

 agriculture have reached a considerable stage of evolution. Here, 

 too, the density of the population and the level nature of the soil 

 permit the growth of those vast despotisms under which alone an early 

 society can be organized with any high degree of internal diversity. 

 But just as navigation, nursed on inland and island-studded seas, 

 spreads afterward to the wider oceans, so agriculture, nursed on well- 

 watered alluvial plains, spreads afterward to drier, rockier, or more 

 mountainous districts. In the desert uplands of the Punjaub, cultiva- 

 tion exists wherever wells can be sunk, even at immense depths, and 



