178 
TUE GEOLOGIST. 
relative level of laud aud sea. They must have beeu formed when 
the laud was higher than it is at present, — perhaps not more than 
200 feet. These submarine peat-bogs may have been formed contem- 
poraneously with the shell-deposit next noticed. 
Some years ago, when dredging on the west side of the Dogger 
Bank, off the coast of Durham, in about 50 fathoms water, the dredge 
brought up a large quantity of dead specimens, in a chalky condition, 
of truncata (Annals Nat. Hist. vol. xviii. p. 233). It is impossi- 
ble to conceive that these specimens of a littoral species lived at the 
depth from which they were procured ; nor can 1 admit that they 
have been transported from a shallower habitat by marine currents. 
There is less difficulty in contending thnt they lived on the spot 
which yielded them, Avhen the Dogger Bauk was a subaerial surface ; 
and that the species ceased to live in the locality when the land be- 
came submerged. 
Third epoch. — Influenced by the investigations of Geikie, also by 
some considerations given in a notice which I have elsewhere ])ub- 
lished (' Parthenon,' Xo. 50, April 11, p. 417), I am led to believe 
that the " Glasgow canoe-sands " are not so ancient as some archaeolo- 
gists have conceived. Possibly some portion of this deposit may be 
of high prehistoric antiquity ; but evidently some of it was formed 
when Scotland was occupied by the E-omans. 
Admitting the view just stated to be correct, it necessarily follows 
that the geological epoch under consideration includes the historical 
era of our country. A question now suggests itself — Are the slight 
vertical movements of the Post- Glacial period equal in chronological 
value to the much larger ones of the Glacial period ? Or another — 
Are they simply equivalents of the minor oscillations which accom- 
panied the great movements of the latter term ? Considering the 
magnitude of the physico-geographical changes which characterized 
the Glacial period, as compared with those of the following one, I 
feel most inclined to adopt the view comprehended in the last ques- 
tion. In this case it may be contended that the Post-Glacial period 
has not yet advanced beyond its initial stages. 
SPECULATIONS ON POSSIBLE PHYSICAL AND COS- 
MICAL PHENOMENA IN KEFERENCE TO THE PAST 
CONDITIONS OF OUR EARTH. 
By S. J. Mackie, F.G.S. 
AVhenever we begin to think about the formation of the universe 
we get at once into the realms of speculation, and the only value of 
our thoughts rests in their probability. In everything unknown we 
must first form an idea — that is, speculate ; then, by partial gather- 
ings of facts, or by positive reasoning, we may theorize. Ultimately, 
by the accumulation of evidence, we may prove that which, in the 
