Oct, Va 1873] 
pated all the more important results of modern cave ex- 
ploration, and how thoroughly he had worked out that 
doctrine of the antiquity of man which the great majority 
of geologists so long attempted to put down. Such 
wholly independent researches as those of Schmerling in 
Belgium, McEnery in Devonshire, and Boucher de 
Perthes in France, made by careful and conscientious ob- 
servers, and all converging to the demonstration of one 
fact, were for many long years laughed at or ignored, 
solely because they clashed with preconceived opinions. 
When this occurred with the students of a science which 
had already fought andjwon many hard battles against 
popular and theological prejudice, and whose whole course 
of study should have taught them how to interpret the 
evidence adduced, we are bound to deal tenderly with the 
less unjustifiable prejudices of those who have had no 
such training. 
Notwithstanding the lesson these long-ignored facts 
should have taught them, some geologists still exhibit a 
strange fear or hesitation in facing the whole results of 
modern inquiries on the subject. How is it that, when- 
ever any estimate is made of the lapse of time (expressed 
in years) since any human remains or works of art were 
deposited, the lowest possible estimate is almost always 
chosen? One would think that, having once got beyond 
the traditional six thousand years, the period of man’s 
past existence would be a matter of purely scientific in- 
quiry, to be arrived at by careful estimates in a variety of 
ways. But how can we possibly arrive at the truth by 
always taking the lowest estimate? we might just as 
reasonably always take the highest. Is there any merit 
in arriving at a false result so that the figures are small ? 
Is it really the “safe” side so to calculate that we shall 
almost certainly be wrong? Astronomers do not think 
those observations most likely to be correct which give 
the smallest distances and sizes of the heavenly bodies 
and it would be more dignified and more scientific if 
geologists, whenever any data exist on which to found a 
calculation, should insist on taking the mean result of 
various impartial estimates as that most likely to be the 
true one. From this point of view it may be interesting 
to give a summary of the more important attempts, which 
have yet been made to determine the antiquity of human 
remains or works of art. 
From observations at the delta of the Tiniére and on 
the lakes of Neufchatel and Bienne, the bronze age in 
Europe has been determined with approximate accuracy 
to have been from 3,000 to 4,000 years ago, and the stone 
age of the Swiss Lake dwellings at from 5,000 to 7,000 
years and an indefinite anterior period. The burnt brick 
found 60 ft. deep in the Nile alluvium indicates an anti- 
quity of about 20,000 years, taking, from a calculation by 
Mr. Horner, the estimate of 3} in. per century as thejrate 
of deposit of the mud. Another fragment found at 72 ft. 
deep is estimated by M. Rosiére to be 30,000 years old. 
Some human bones found in a lacustrine formation in 
Florida have been considered by Agassiz, after a careful 
examination of the locality, to be at least 10,000 years 
old. A human skeleton found at a depth of 16 ft. below 
four buried forests superposed upon each other, has been 
calculated by Dr. Dowler to have an antiquity of 50,000 
years. 
These latter estimates may be very uncertain, but 
NATURE 
463 
we have no reason to think them improbable, from 
what we know of the great changes of physical 
geography that have undoubtedly taken place since 
man existed. Kent’s Cavern at Torquay furnishes a 
good example of these, since the whole drainage of the 
surrounding country must have been very different when 
the great thickness of cave earth was deposited by floods 
rushing through the cavern which is now situated in an 
isolated hill. We have here indications of an immense 
antiquity from various sources, The upper stalagmitic 
floor itself marks a vast lapse of time, since it divides the 
relics of the last two or three thousand years from a 
deposit full of the bones of extinct mammalia, many of 
which, like the reindeer, mammoth, and glutton, indicate 
an arctic climate. It has been remarked that the varying 
thicknesses of the stalagmitic floor, from 16 in. to 5 ft. and 
upwards, closely correspond to the present amount of 
drip in various parts of the cave, so that the cave itself 
with its various fissures and crevices does not ‘appear to 
have been materially altered since the stalagmite was 
deposited. It is true that the drip may once have been 
greater, but it may also have been less, and we do not 
know that a more copious drip would necessarily produce 
amore rapid deposit of stalagmite. But names cut into 
this stalagmite more than two centuries ago are still 
legible, showing that, in a spot where the drip is now 
very copious, and where the stalagmite is 12 ft. thick, 
not more than about one-eighth of an inch, or say one- 
hundredth of a foot, has been deposited in that length 
of time (British Association Report, 1869, p. 196). This 
gives a foot in 20,000 years, or 5 ft. in 100,000 years ; and 
there is no reason whatever to consider this to be too 
high an estimate to account for the triple change of 
organic remains, of climate, and of physical geography. 
But below this again there is another and much older 
layer of stalagmite, generally broken up and imbedded in 
the cave earth. This older stalagmite is very thick and 
is much more crystalline than the upper one, so that it 
was probably formed at a slower rate. Yet below this 
again, in a solid breccia, very different from the cave 
earth, undoubted works of art have been found. A fair 
estimate will therefore give us, say, 100,000 years for the 
upper stalagmite, and about 250,000 for the deeper layer 
of much greater thickness, and of more crystalline texture. 
But between these we have a deposit of cave-earth which 
implies a different set of physical conditions and an altera- 
tion in the geography of the surrounding country. We 
have no means of measuring the period during which this 
continued to be formed, but it was probably very great ; 
and there was certainly some great change in physical 
conditions during the deposit of the lower stalagmite, 
because the fauna of the county underwent a striking change 
in the[interval. Ifwe add 150,000 years for this period, 
we arrive at the sum of half a million as representing the 
years that have probably elapsed since flints of human 
workmanship were buried in the lowest deposits of Kent’s 
Cavern. It may be objected that such an estimate is 
so loose and untrustworthy as to be altogether valueless ; 
but it may be maintained, on the other hand, that such 
estimates, if sufficiently multiplied, are of great value, 
since they help us to form a definite idea of what kind 
of periods we are dealing with, and furnish us with a 
series of hypotheses to he corrected or supported by 
