Vol. 58.] AMONG THE JURASSIC ROCKS OF SUTHERLAND. 309 
side into the area of denudation, previous to the new depression ; or, 
possibly, that the Oxfordian deposits are there, and that the inlier 
fell over on to them from the neighbouring cliff. 
VII. Conctupmne ReMaARKs. 
It must not be supposed that all the concordances herein pointed 
out between the actual phenomena of the breccia-beds, and the 
known or probable results of an ice-foot, are essential to the exist- 
ence of a relationship between the two—a caution rendered necessary 
by experience. Several of the phenomena noted might be proved to 
be due to other causes; but the result would only be to weaken the 
evidence, in proportion to their importance, though not to destroy it. 
For that purpose, some such must be found incompatible with the 
origin suggested. This must be difficult, owing to the wide range 
of variation permissible in an ice-foot deposit. It may be found 
where it first accumulates, or be carried elsewhere: it may ultimately 
rest crowded on a shore, or scattered over the sea-tloor: it may 
contort the strata then forming at the place of its rest, or the 
fragments may fall gently. It may contain some rounded stones, 
and even afew scratched ones. They may rest one against the other, 
or be separated. They may be very large or small. There may be 
signs of stratification of the finer material in parts. The beds may 
be thick or intermittent, widespread or local. 
The essential features of an ice-foot deposit are that the bulk of 
the stones of which it is composed should be angular, of various 
sizes, without order, definite position, or internal bedding.’ Each 
separate deposit would have no more variation in the nature of the 
contents than could be expected in a single cliff. The breccia-beds 
of Sutherland possess these features, and in addition other less 
essential ones ; and are thus proved to have originated in an 
ice-foot, and they are the first recognized in this 
country as having such an origin. 
The word ice-foot has been used by Mr. Mellard Reade ? for the 
agent that he supposed to have transported some gigantic boulders 
of the Kastern Midlands, but his definition of it as ‘ pack-ice.. ... 
frozen into a sheet or ice-foot,’ shows that he is not referring to 
the ice-foot of Col. Feilden & Mr. De Rance. 
On the other hand, the phenomenon has been described, without 
the use of the name, at that time (1873) unknown, by Prof. Sollas & 
Mr. Jukes-Browne, as shown by the Cambridge Greensand. Here 
there is no ice-foot melting am sztu, but only an ice-foot-contribution 
to a distant deposit. This is shown by the characters assigned to 
the fragments. ‘ Most of them are subangular,’ ‘ many of them are 
of large size. ‘The majority present no signs of ice-scratches,’ 
These seem to be contributions from several localities, as the frag- 
ments ‘are of very various lithological characters’; but a good 
' See exception above (p. 306). Alsoin the case of the fragments dropping 
at sea, they would descend with their centre of gravity in its lowest position. 
* Quart. Journ. Geol. Soc. vol. xxxviii (1882) p. 233. 
YZ 
