mation near
New Kaye--Inference from such Formation--Tour resumed--Loch of
Stennis--Waters of the Loch fresh, brackish, and salt--Vegetation
varied accordingly--Change produced in the Flounder by fresh
water--The Standing Stones, second only to Stonehenge--Their
purpose--Their Appearance and Situation--Diameter of the
Circle--What the Antiquaries say of it--Reference to it in the
"Pirate"--Dr. Hibbert's Account.

We returned to Stromness along the edge of the cliffs gradually
descending from higher to lower ranges of prepices, and ever and anon
detecting ichthyolite beds in the weathered and partially decomposed
strata. As the rock moulders into an incoherent clay, the fossils which
it envelops become not unfrequently wholly detached from it, so that, on
a smart blow dealt by the hammer, they leap out entire, resembling, from
the degree of compression which they exhibit, those mimic fishes carved
out of plates of ivory or of mother-of-pearl, which are used as counters
in some of the games of China or the East Indies. The material of which
they are composed, a brittle jet, though better suited than the stone to
resist the disintegrating influences, is in most cases greatly too
fragile for preservation. One may, however, acquire from the fragments a
knowledge of certain minute points in the structure of the ancient
animals to which they belonged, respecting which specimens of a more
robust texture give no evidence. The plates of Coccosteus sometimes
spring out as unbroken as when they covered the living animal, and, if
the necessary skill be not wanting, may be set up in their original
order. And I possess specimens of the head of Dipterus in which the
nearly circular gill-covers may be examined on both surfaces, interior
and exterior, and in which the cranial portion shows not only the
enamelled plates of the frontal buckler, but also the strange mechanism
of the palatal teeth, with the intervening cavities that had lodged both
the brain and the occipital part of the spine. The fossils on the top of
the cliffs here are chiefly Dipterians of the two closely allied genera,
Diplopterus and Osteolepis.

A little farther on, I found, on a hill-side in which extensive
slate-quarries had once been wrought, the remains of Pterichthys
existing as mere patches, from which the color had been discharged, but
in which the almost human-like outline of both body and arms were still
distinctly trac