28 THE GEOLOGY OF BERMUDA. 
beneath for some inches in depth, though less hard than the superficial 
crust, is more firmly consolidated than the surrounding rock. The ob- 
jects accordingly appear, when the surrounding rock is removed by 
weathering or otherwise, as irregular cylinders. It has often been 
crudely supposed that these cylinders are petrifactions or casts of the 
trunks of the palmetto; but this is certainly erroneous. I believe, how- 
ever, that this error is but a misconception of the truth. The base of 
the palmetto stem is convex, with numerous small roots radiating from 
its surface. Its form is the counterpart of the shallow cup, pitted with 
little depressions, which is the characteristic feature of the bodies in 
question. The true explanation of the formation of these bodies appears 
to be simply this: the rain-water trickles down around the convex base 
of the palmetto stem, and thence follows the little radiating roots. As 
in the other cases already discussed, the course of the waters is marked 
by a more perfect cementing of the grains of calcareous sand, giving 
the rock in those parts a sub-stalagmitic character. When the tree 
finally dies, and drops out of its socket, there is left a saucer-shaped 
cavity, lined by a sub-stalagmitic crust, and an irregular cylinder of 
Somewhat hardened rock beneath it. Sir Wyville Thomson combats 
the idea of the organic origin of these bodies, and calls attention to the 
frequent irregularity of their form. He tells us that a perfect series of 
gradations may be traced from the regular circular form (‘‘the most 
characteristic, and probably by far the most common”)* to forms so 
irregular that their organic origin is entirely out of the question. Now 
in maintaining that the common and typical sort of these bodies are 
produced by the rain-waters following the course determined for them 
‘by the stem of the palmetto, I by no means deny that by accidents of 
a totally different sort special channels for the percolating waters may 
‘be determined, and “calcareous concretions” produced of all sorts of 
irregular forms. Moreover, it would be the most natural thing in the 
world that some of the concretions whose form is determined by other 
conditions should considerably resemble some of the least regular and 
perfect of those formed in the way I have explained. Admitting that 
all the ‘‘concretions,” regular and irregular, are the result of the un- 
equal hardening of the stone by the cementing action of water, the regu- 
lar saucer-shaped cavities already described are so frequent and so 
characteristic that it is worth while to inquire what is the special con- 
dition which has hardened the rock in precisely that form. That ques- 
*Thomson, op. cit., Vol. I., p. 308. 
