Here and there along the Green gush out bright fountains of delicious water from artesian wells driven into the "greensand," some 200 feet below the surface. Throughout all its length the village is sheltered, on the north, by the ridge of White Hill, while, on the south, the orchards and closes with their "hedge-row elms," slope down to the Cam and its water-meadows. The stream here runs beneath a gravel-terrace of its own formation, which has proved exceptionally rich in the remains of pleistocene mammalia, mostly, as has been said,[175] connoting a semi-tropical climate. Specimens of elephant, hippopotamus, rhinoceros, bison, urus, lion, bear, hyaena, derived from Barrington, are to be seen in the Sedgwick Museum at Cambridge. Associated palaeolithic flint implements, and red-deer antlers rudely cut, show that human intelligence existed here along with these monsters, at least 5000 years ago, at the lowest estimate, which some geologists multiply fifty fold; and excavation has shown that the site has been populated pretty well ever since. Neolithic, British, Roman, Anglo-Saxon, and Mediaeval relics have here been unearthed in quite astonishing abundance; and, though no Roman villa has yet been located, Roman coins have been found literally by the hundred. [Footnote 175: See p. 221. The gravel here is older than that at Grantchester.] This wealth of finds has been largely due to the "coprolite" digging, as it was inaccurately called, which went on here (and throughout the neighbourhood) during the whole latter half of the nineteenth century. It had been discovered that the "upper greensand"[176] (here a narrow deposit immediately over the gault and usually some fifteen or twenty feet below the surface) was full of organic remains worth extracting for manure. These remains were never true coprolites, but mostly formless nodules rich in phosphate of lime, many being sponges, along with abundance of sea-urchins, mollusca, crabs, and innumerable sharks' teeth. [Footnote 176: So called because full of green grains of "glauconite," which appear to be the internal casts of the shells of foraminifera. This bed, however, is not the true Upper Greensand, but "riddlings" from it.] The industry brought a wave of prosperity to the district; for coprolites were worth some L3 per ton, and the average yield was some 300 tons per acre. The merchants were, therefore, willing to pay well for the privilege of digging them out, and usually offered the landowner L150 or more per acre for three years' occupation of the land (more than its capital value); being bound also to level and resoil it at the end of their tenancy. Wages, too, ran high; a good "fossil-digger" could earn his 40_s_. per week. This produced a corresponding rise in agricultural wages, which went up from 10_s_. or 12_s_. per week to double that amount. The fossil-digging was all piecework, the men being paid by the cubic yard of earth moved.