and
on the extreme precariousness of the tenure on which the existence of
its numerous denizens was held. In a section of little more than a
hundred yards there occur at least two platforms of violent
death,--platforms inscribed with unequivocal evidence of two great
catastrophes which over wide areas depopulated the seas. In the Old Red
Sandstone of Caithness there are many such platforms: storey rises over
storey; and the floor of each bears its closely-written record of
disaster and sudden extinction. Pompeii in this northern locality lies
over Herculaneum, and Anglano over both. We cease to wonder why the
higher order of animals should not have been introduced into a scene of
being that had so recently arisen out of chaos, and over which the reign
of death so frequently returned. In a somewhat different sense from that
indicated by the poet of the "Seasons,"

"As yet the trembling _year_ was unconfirmed,
And _winter_ oft at eve resumed the gale."

Lying detached in the stratified clay of the fish-beds, there occur in
abundance single plates and scales of ichthyolites, which, as they can
be removed entire, and viewed on both sides, illustrate points in the
mechanism of the creatures to which they belonged that cannot be so
clearly traced in the same remains when locked up in stone. There is a
vast deal of skilful carpentry exhibited--if carpentry I may term it--in
the coverings of these ancient ichthyolites. In the commoner fish of our
existing seas the scales are so thin and flexible,--mere films of
horn,--that there is no particularly nice fitting required in their
arrangement. The condition, too, through which portions of unprotected
skin may be presented to the water, as over and between the rays of the
fins, and on the snout and lips, obviates many a mechanical difficulty
of the earlier period, when it was a condition, as the remains
demonstrate, that no bit of naked skin, should be exposed, and when the
scales and plates were formed, not of thin horny films, but of solid
pieces of bone. Thin slates lie on the roof of a modern dwelling,
without any nice fitting;--they are scales of the modern construction:
but it required much nice fitting to make thick flagstones lie on the
roof of an ancient cathedral;--_they_, on the other hand, were scales of
the ancient type. Again, it requires no ingenuity whatever, to suffer
the hands and face to go naked,--and such is the condition of our
existing fish, with their s