1866. | Geology and Palzontology. 283 
was probably slightly upheaved ; the area was then depressed be!ow 
the sea-level, and sea-mud with shells of Serobicularia piperata 
was deposited ; again the land was upheaved, and the surface of the 
mud was converted into meadow. Lastly, a small depression of 
the surface caused the accumulation of the shingle-bank on the 
meadow-land. We have thus, in this paper, a beautiful example 
of the manner in which even the smallest oscillations of level may 
be traced, in comparatively insignificant deposits, by the practised 
geologist. But Mr.Godwin-Austen makes still further use of the 
evidence he has obtained. The Angular Detritus he finds to be 
the same as that which overlies many of the so-called ‘“ Raised 
Deaches,” such as that between Braunton and Bagey Point ; conse- 
quently, “in a modified sense,” these sea-beds or raised beaches are 
Pre-glacial, or older than the period of deep surface-disintegration. 
This “ modified sense” is really “ homotaxis ;” for the author observes 
that “just as the amount of northern depression increased from 
the south northwards, so the progress of that depression was in the 
contrary direction, or from north to south. The line of the Bristol 
Channel was nearly the limit of this submergence, and was the last 
reached.” Respecting the age of the deposits above the Angular 
Detritus, and the value of the indications they afford, Mr. Godwin- 
Austen remarks, “that they belong to the time of our existing 
assemblage of animals and plants, that they indicate changes of 
small vertical amount, and are remarkably uniform.” 
In a former Chronicle,* we gave a sketch of Mr. Jamieson’s 
ice-dam theory of the Parallel Roads of Glen Roy, and we have now 
to notice a paper by the Rey. R. Boog Watson in contravention of 
that theory, and in support of Mr. Robert Chambers’s view of their 
marine origin, chiefly on the grounds that the sea has been on the 
spot and is capable of performing the work required. The author's 
main objections to the ice-dam theory are—(1) that terraces similar 
to the Parallel Roads, though less perfect, exist at all levels round 
our coasts, as well as inland, along every fjord in Norway, and across 
the whole of Sweden; (2) that there are several terraces, even in 
Lochaber, unconnected with any “col ;” and (3) that to provide the 
mass of ice required for the dams, the relation always observed to 
exist between glaciers and the snow-field which feeds them, would 
have to be reversed ; that is to say, the snow-field would be minute 
and the glaciers gigantic. Mr. Watson also contends that the ice- 
dam theory treats the Parallel Roads as something distinct from 
other terraces, whereas he considers them specifically the same, the 
Glen Roy Roads differing only in being more perfectly preserved. 
The absence of fossils from the Parallel Roads is admitted to be a 
difficulty in the way of the“ Marine Theory ;” but Mr. Watson 
explains it by showing that it “ accords with the character of simi- 
* ¢ Quarterly Journal of Science,’ vol. i. p 292. 
