4.02 WARREN UPHAM, ESQ., M.A., F.G.S.A., ON 
(or Chellean, from Chelles near Paris); 2, Mousterian, from 
Le Moustier in Dordogne; 38, Solutrian, from Solutré in 
Burgundy; and, 4, Magdalenian, from the caves of La 
Madeleine in Dordogne. These time divisions are 
characterized by increasing variety and excellence of the 
implements made, and by concomitant changes of the fauna. 
The implements found in the Somme valley are referable 
only to the earliest stage, which had at first a mild and 
moist climate, changing afterward to severe cold, with thick 
ice on the rivers in winter, broken and floating large blocks 
of rock in spring. 
Let us now examine the geologic origin and deposits of 
this valley in their relation to these stages of archeologic 
development, comparing both records with the ascertained 
history of the Ice age in the British Isles and northern 
Europe, and with estimates of its duration and that of the 
Postglacial period. 
Above Amiens the Somme basin has been eroded to an 
undulating surface of broad but low hills and ridges, and is 
drained by several streams which converge in and near that 
city, bemg the sources of the supply of the Pleistocene 
eravels extensively excavated at St. Acheul, St. Roch, and 
Montiers, which are situated respectively in the south- 
eastern, western, and north-western environs of the city. 
From Amiens to the sea, a distance of about forty miles, the 
valley is troughlike, with a bottomland from a half-mile to a 
mile and a half in width for nearly twenty-five miles, extend- 
ing down to Abbeville, and thence widening to three or four 
miles at its mouth, inclosed usually by very gentle or 
moderately steep slopes, but in a few places bordered by a 
steeper or precipitous bluff formed through direct under- 
mining by the river at some time during the slow process of 
the valley erosion. 
The river at Amiens is about 65 feet above the mean tide 
sea level; at Montiers, 58 feet; and at Abbeville, about 15 
feet, the high tides having formerly reached above the city, 
until held back by the engineermg improvements of the 
river course which now restrict its once meandering and 
dividing waters to a single straight canal along its next nine 
miles. The bottomland is mostly no more than 2 to 5 feet, 
and in its highest parts about 10 feet, above the river 
in its ordinary low water stage. Along nearly all the 
distance below Amiens it has large tracts of peat, from 10 to 
30 feet in depth, thus extending far beneath the level of the 
