178 



THE GEOLOGIST. 



relative level of laud and sea. They must have been 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 Mya trwicata (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 that they lived on the spot 

 which yielded them, when the Dogger Bank 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 pub- 

 lished ('Parthenon,' No. 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 Romans. 



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 REFERENCE TO THE PAST 

 CONDITIONS OF OUR EARTH. 



By S. J. Mackie, F.G.S. 



Whenever 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 

 mu«t 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 



