169 
former.* * * § It is more properly a magma (or tufa, as McEnery 
calls it) into which a stick may be thrust to a considerable 
depth ; and consists of lime united with carbonic acid, and 
associated intimately with iron (peroxide) in such sense that 
it is apparently impossible at the usual atmospheric pressure to 
re-dissolve the mass in any quantity of water acidulated with 
carbonic acid; the oxide of iron being, of course, entirely 
insoluble, as will be seen by the analysis I present. f 
How, then, should the immense mass of material forming 
this floor have been dissolved by rainwater, and infiltrated 
through the rocky roof of the cavern ? J This solvent could not 
have extracted the iron from the superincumbent earth unless 
it there exists at a lower state of oxidation, which I do not 
think probable, and had no means of examining (the hill above 
the cave is laid out as a garden, beneath which I am told the 
labourers can be heard at their work) . I certainly was led to sus- 
pect the existence of a thermal spring, which containing as usual 
iron in solution at a lower stage of oxidation, as well as lime, 
might have gained entrance in some way into the cavern. It 
is not my business to find the explanation, but to insist on this, 
that a mass of so uncertain origin which (as we may see pre- 
sently) need not to have been produced as stalagmite at all§ 
cannot be reckoned upon in any sense as a chronometer of time. 
So much for the upper stalagmite floor, which was from 
sixteen to twenty inches thick, sometimes attaining five feet, 
and containing large fragments of limestone, a human jaw, 
and the remains of extinct animals. During the long period 
of years which this took in forming, || it seems that only 
one human being left his remains in the cretaceous mass. If 
* Mr. McEnery very appropriately observes that in some parts of the 
cavern the stalagmite and stalactite had been formed by the percolation of 
water “ through the rents or pores of the rode.” The rock itself, as seen by 
the specimen I exhibit, is impermeable to water ; in other parts ‘ ‘ the 
calcareous moisture entered laterally through the clefts and crevices, and spread 
slowly over the floor,” — Literature of Kent’s Cavern, pp. 41, 42. 
t “ After rains these infiltrations are copious, and in some places coloured 
with a solution of red marl or vegetable soil.”— McEnery, p. 282. 
X In their first report the Committee say, “Since the commencement) 
the work unusually heavy rains have fallen in the district, but water has 
entered through the roof at very few points only.” 
§ Mr. McEnery says in other places the drop from the roof acted con- 
currently with the oozings from the sides in forming the floor, which conse- 
quently partakes of both manners. — Lit. of Cave, p. 42. 
[| In Notes on Recent Notices of the Geology and Palaeontology of Devon- 
shire, Part i. p. 37, read at Teignmouth, July 1874, I find that “the human 
jaw was near the base of the stalagmite.” This was 20 inches in thickness, 
and reckoning “ 500 years for each inch of the stalagmites,” we verge 
upon 100,000 years for the era of this human being. 
