AID RENDERED BY PHOTOGRAPHY TO GEOLOGY. 
29 
ON SOME AID RENDERED BY PHOTOGRAPHY 
TO GEOLOGY. 
BY W. JEROME HARRISON, F.G.S. 
Photography has rendered aid, in turn, to nearly all of the 
sciences, but I wish to note here just three cases which have 
lately come under my notice where it has been specially 
serviceable to geology. 
In 1858 the question of the antiquity of man was brought 
prominently before the public by the discovery of flint instru¬ 
ments, clearly fashioned by human hands, in certain gravel- 
beds at St. Acheul, a suburb of the town of Amiens, in the 
north of France. These gravel-beds were deposited at some 
former period by the River Somme, but as the river now runs 
at a level ninety feet below these old gravels, it was admitted 
by all that the gravels were of very great antiquity. Besides 
the flint tools, these gravels contained many bones of animals, 
some of extinct species, such as the mammoth, cave-bear, &c. 
The French archaeologists, M. Boucher de Perthes and Dr. 
Rigollot, had already collected hundreds of these flint imple¬ 
ments from the gravel-beds when the question of their age 
was brought before the geological world. The leading men of 
science, both of England and France, were not at all prepared 
to accept the evidence afforded by the flint implements with¬ 
out strict investigation, and some of them,indeed, pooh-poohed 
the thing altogether. They insisted that the flints might 
have been made by the workmen engaged in the gravel-pits 
for the sake of the recompense they obtained when they found 
one (and certainly it was true that all the specimens hitherto 
discovered had been purchased from the men, or picked up on 
the floor of the pits). Others, more generous, believed in the 
authenticity of the specimens, but suggested they had been 
dropped down to the depth in the gravel-beds at which they 
were found, either by a settling of the strata, or through some 
crevice in the beds. 
It was to settle this most interesting question that Mr. 
Prestwich (till lately Professor of Geology at Oxford) visited 
Amiens in the autumn of 1858. He superintended fresh excava¬ 
tions by the workmen, and shortly had the pleasure of 
uncovering with his own hands the end of a fine, well-shaped 
flint hatchet, lying at a depth of seventeen feet from the surface. 
This was convincing enough for Mr. Prestwich, but he wanted 
