54 
« In one case, however, M. Boucher de Perthes observed several flat dishes 
of Roman pottery, lying in a horizontal position in the peat, the shape of 
which must have prevented them from sinking into or penetrating through 
the underlying peat. Allowing about fourteen centuries for the growth of 
the superincumbent vegetable matter, he calculated that the thickness gamed 
in a hundred years would be no more than three French centimetres. This 
rate of increase (Sir Charles Lyell added) would demand so many tens of 
thousands of years for the formation of the entire thickness of 30 feet, that we 
must hesitate before adopting it as a chronometric scale.” 
It was obvious that 0-03 metres in a century required upwards of 33,000 
years to give the 10 metres, which in some places existed in the Somme 
Valley. The point he would lay stress upon was, that the hesitation to accept 
this should not have been made to arise from the result which it gave, but 
from the fact that the data were so obviously worthless for forming any 
calculation at all. The absolute but erroneous assumption that continual 
formation of peat went on at one uniform rate, was the basis of the whole 
argument. This pottery was found, so it was stated in M. Boucher de 
Perthes’ book ( Antiquites Geltiques, ii. p. 135), to be 0*60 metres (nearly 
2 feet) below the surface. This writer argued further that much of the peat 
being impure, the factor had to be reduced to one-fourth, i.e., to 0*45. Now, 
Samian pottery, it was argued, must be 1,400 or 1,500 years old. It was 
assumed ( a ) that at that distance of time it was (6) placed gently on the 
surface of the turbary so as not to sink through, and (c) circumstances were 
such that it was not buoyed up, and (d) that the peat from that moment 
down to 1863, had gradually, and at one uniform rate per annum, grown over 
it. Any one of the conditions of course being liable seriously to aflect the 
factor, they were supposed to accept all, and thereby obtain a factor to apply 
generally to the growth of the peat throughout the Somme Valley. If this 
was not what was meant by Sir Charles Ly ell’s argument, nothing could be 
gleaned from it at all. The lecturer then proceeded to consider the next 
elements for the computation of the time which had elapsed since the 
deposition of the implement-bearing beds. Without quoting new passages, 
the words already given showed the line of argument, namely, “ that the peat 
was posterior to the time when the valley was excavated through the 
gravels.” . . 
It was in vain to look for any figures of computation. for such excavation, 
although elsewhere in Sir Charles Lyell’s book (p. 367) it was intimated that 
the upper and earliest of these gravels were the equivalents probably of beds 
100,000 years old, no arguments were forthcoming as to the means of compu- 
tation. Indeed, it seemed beyond all calculation. Imagine the rate at which 
a trickling stream could excavate and grow into a large one, and carry down 
the material of a valley 115 miles long, and varying from one mile to ten 
miles broad. Imagine the millions upon millions of tons of chalk and of 
other material to be scooped out and carried along and deposited in the sea. 
The time was certainly beyond all calculation, and the 67,000 years, he was 
sure, would be found by any one who considered the problem carefully to 
represent but a mere unit in the time required under the circumstances. 
But then the question forced itself on one, “Was the Somme Valley 
excavated by the Somme River at all?” Not one line would be found, m 
evidence ; it was assumed purely and absolutely, and on that assumption 
alone were based all the arguments as to time, which were put forward. 
In considering the hypothesis of the excavation of a valley of this kind by 
means of a river, the first question to be asked was naturally, “ Where did 
the water come from? ” Considering the vast surface to be removed, it was 
necessary to have a supply of water of enormous quantity and of constant 
flow. And much more than that, it was necessary to have an impetus given to 
that water by a fall or gathering together of streams to give it force sufficient 
