200 REY. A. IRVING, D.SC., B.A., ON 
but it is easily accessible. As regards the time-age of Man (in 
the wider sense) on this planet, much (1 have pointed out, loc. 
cit ) depends upon our definition of the terms JM/an and Homo, 
and I give reasons for bringing down Dr. Astley’s positive 
assertion that its duration reaches 80,000 to 120,000 years,* to 
something more like a fourth of such estimate. To me, asa 
geologist, it seems preposterous to build up a piece of theory— 
as Dubois has done—upon such flimsy evidence as he has been 
able to produce. We have no evidence even that the anthropoid 
fragments which he found belonged to the same individual ; and 
it may be seriously questioned, whether, in the want of a 
geological survey, the assignment of the deposits in which those 
remains were found to the later Tertiary is anything more than 
guesswork, Weare not justified in reasoning from the recognized 
succession of superficial deposits in Europe, where the glacial 
epoch furnishes us with something like a definite horizon, to an 
unsurveyed region in the heart of the Tropics. Anyone, 
moreover, who has hke myself recently been engaged in an 
investigation involving exact correlation of later deposits, in 
which the later Tertiaries shade off in some regions into the 
Quaternary, as in Britain the post-glacial Pleistocene shades off 
into Post-pleistocene and recent alluvial deposits, knows how 
exceedingly difficult it is to get conclusive evidence as to the 
exact place in the time succession of a given superficial deposit, 
where redeposition has often to be allowed for, unless we can 
get clear evidence derived from contemporaneous fossils, and 
can make pretty sure that such remains as occur are not 
derived from older strata. I am not aware that anything like 
such conclusive evidence has been brought forward by Dubois 
for his Pithecanthropus erectus. 
During the past year the scientific world has had its curiosity 
aroused by the announcement of the discovery of a massive 
human jaw under some 80 to 90 feet of stratified diluvial sand 
at Mauer in the Neckar Valley, near Heidelberg—a locality 
with which I am pretty familiar. There is an excellent model 
of the jaw in the Geological Department of the Museum of 
Natural History at Kensington, with a modern human jaw 
placed above it for comparison. To Dr. C. W. Andrews, F.R.S., 
who kindly drew my attention to it, I am indebted for a perusal 
of Schoetensack’s Monograph on this supposed late Tertiary 
“man,” which he named Homo heidelbergensis. It is a 
magnificent piece of descriptive woik; but unfortunately the 
Following Prof. T. Rupert Jones, F.R.S., and others of the Lyell School. 
