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hogshead, in one cavity, of a sweetish taste, but accompanied with a 
vitriolic, or iron-like twang*. 
Dr. Woodward, speaking of some specimens of enhydri, saysf, 
“ they were found, amongst many others, in sinking the wells in 
Caen- Wood, whence that water, which we call the Hampstead water, 
is derived. — I was down only in one of the wells, which they were 
then in digging ; but I saw several of these enhydri, with a pretty 
many pyrites, amongst the earth that was flung forth of the other 
wells. They are of several sizes, from the bigness of a walnut, to 
about two feet in breadth. They are generally of a compressed 
shape ; and lessen, or grow thinner, towards the edge, or ambitus, 
of them. Those that I saw, lay about fifteen or sixteen feet deep, 
in a stratum of sandy clay. The surfaces of that stratum, and the 
flats or larger plains of the enhydri, lay parallel and level: they 
were all hollow, and usually divided into several cells; but these 
were uncertain, in their number, figure, and capacity. The parti- 
tions of the cells were rarely very thick. The outer coat was in 
some double, in others triple, and in a few quadruple ; as consisting 
of two, three, or four strong crusts, involving and carrying one 
another. The cavities or cells were generally near full of an insipid 
coagulnm, or liquor, about the consistence of cream, though in here 
and there one, it was a little thicker. ’Twas most commonly of a 
greyish colour ; but in some few Twas of a bluish, and in others 
of a blackish hue.” 
Whether it be believed, that these several bodies owe their exist- 
ence to fire or water, it will, I conceive, be equally admitted, that 
thay have been formed in cavities previously existing in the matrix, 
in which they are contained. I suppose, then, that one of these 
cavities becomes filled, by some small aperture, with a liquid 
* The Natural History of StafiFordshire, by Robert Plott, LL. D. 1686 . 
^ An Attempt towards a Natural Historj' of the Fossils of England, by J. Woodward, M. D. 
