der favorable circumstances dried, hardened, and formed a rock of
greater or less solidity. Our colleague, Dr. Gould, has exhibited to
us a specimen of dried clay from the shores of the Bay of Fundy,
containing beautiful impressions, recently made, of the footsteps of
birds. The particles brought by the waves, and deposited in the manner
described, were derived from the destruction of other rocks previously
existing, particularly granite and flint, or silex, the shining atoms
of which compose no small part of the sandstone rock.

It is easy to conceive, that, while these deposits were taking place
in the soft condition, portions of vegetable matters might become
intermixed; and that these, with the impressions of the feet and other
parts of animals and unorganized substances, might be preserved by the
process of desiccation. The agency of internal heat may have also been
employed in some cases in baking and hardening these crusty layers.

The sandstone rock, though in some places actually in a state of
formation at the present time, lies in such a manner in the earth's
crust as to indicate an immense antiquity. The age of these beds
varies in different situations. The sandstone rocks which contain the
greater part of the impressions are called _new red sandstone_, to
distinguish them from the _old red_, which is of a greater age. The
deposits on Connecticut River may not be attributed to the action of
this river, but are of higher antiquity, probably, than the river
itself, and proceeded from the waves of an ancient sea, existing in a
state of the surface of the globe very different from that of the
present day.

In 1834, tracks were discovered near Hildberghausen in Saxony, to
which Prof. Kaup, of Darmstadt, gave the name of Chirotherium, from
the resemblance to the impressions of the human hand. On a subsequent
examination, Prof. Owen preferred the name of Labyrinthodon, from the
resemblance of the folds in the teeth to the convolutions of the
brain.

Various other instances of impressions were seen; and, in the year
1835, Dr. Deane and Mr. Marsh, residents of Greenfield, noticed
impressions resembling the feet of birds in sandstone rocks of that
neighborhood. These observations having come to the knowledge of
President Hitchcock, of Amherst College, that gentleman began a
thorough investigation of the subject, followed it up with unremitted
ardor, and has, since 1836 (the date of his first publication), laid
bef