CHAPTER 111 
THE DISCOVERY OF PRE-NEOLITH IC MAN 
In tracing the various kinds of men who lived in the 
Neolithic period, the open country, the river valleys, and 
the submerged land surfaces served us very well. When, 
however, we try to follow man beyond the bounds of the 
Neolithic period— when the Thames was depositing the 
deepest layers of ballast gravel in her ancient bed — we 
must seek sequestered nooks where the earth keeps a 
more orderly register of events than in the turmoil of 
flooded valleys. The ideal place we seek is a cave, 
particularly a limestone cave, for the drip from the roof, 
laden with lime salts, seals up with a covering of stalag- 
mite any bones which chance to lie on the floor. The 
floor of such a cave is always having additions made to 
it. If men make their hearths on it, human debris ac- 
cumulates. Chips and dust are always falling from the 
roof ; the mud washed in by rain or flood is added to 
other accumulations. In course of time the floor may 
grow until it actually reaches the roof, thus obliterating 
the cave. If no living thing has visited the cave as it 
became filled up, then the strata of the floor are " sterile " ; 
but if men have used the cave as a habitation or as a 
passing shelter, or if they chance to die there, then the 
earth-buried stratum of the. floor becomes a page of 
history. It has taken us nearly a century to understand 
that caves may contain historical documents of the most 
precious kind. By a study of cave records, we have come 
by a knowledge of the races who preceded the men of 
the Neolithic period — the races of the Palaeolithic period. 
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