186 EF. Andrews on Human Antiquities at Abbeville, ée. 
! 
thousands of localities in the United States, are formed as fol- 
WS: e annual crop o its, twigs, leaves, and windfall 
trunks, furnished by the trees and shrubbery of a dense swamp, 
amounts to an immense mass of vegetable matter. These added 
to a thick undergrowth of , herbs, and moss, are all pressed 
against the ground by the winter snows. In the spring they 
are flooded and protected from decay. In the summer they are 
partly protected from oxygenation by the extreme wetness of the 
soil into which they have been pressed. Hence they are only 
slightly rotted when they are finally covered up by the fall of the 
next autumn’s crop. To one who studies the actual quantity of 
this material, a growth of two or three feet in a hundred years is 
_ by no means incredible, Thus the increase of the peat depends 
upon the presence of the forest; but the valley of the Somme 
has lost its forests centuries ago. It is wholly reduced to cul- 
tivation and pasturage, Hardly an ounce of grass or a stick 
of wood ever rots upon it, but every particle of vegetable mat- 
ter is removed for the use of the inhabitants. About Amiens, 
- the ground is all drained, and used for market gardens, and in 
other parts it is all sown with crops, mown for hay, or graz 
for pasture, The peat growth, therefore, is arrested for want 
of material, and no further increase will be observed though» - 
million years should elapse. Hence all calculations of age, 
based on the present want of progress, are necessarily erroneous. 
In the excavations of the peat, Boucher de Perthes distin- 
guishes near the surface relics of the middle ages: below that 
_ to the depth of about six feet Roman and Gallo-Roman remains, 
and underneath that, pure Gallic and other earlier traces. 
ve no means of knowing how long ago the forests of the 
Somme disappeared, but I presume those s occupied by 
Rorhan garrisons would be among the larger settlements, and 
be earliest cleared of timber. Probably the places where Roman 
remains are found may have been destitute of timber, and pro- 
duced little or no peat for the past six or seven hundred years. 
If so, the deposit of six feet of peat over the earliest Roman 
remains was accomplished in about 1200 years, or at the rate 
of about six inches in a century. This is much less than the 
rate required to preserve a stump three feet in height, but the 
iches per century indicated by the depth of the Roman remains. 
If. this be taken’ as'a -probdke standerdthe age ones 
bed, whose thickness is about 26 feet, would be not far from 
