Vol. 58. | {MONG THE JURASSIC ROCKS OF SUTHERLAND. B07 
f will be 
| are 
more crowded with the deposits of successive 
(10) The most southerly deposits the thinner and more isolated, and 
the northern ae be l 
seasons. 
{ Any fragments detached from the ice while floating will sink 
| The fragments in the thinner breccia-beds have sunk 
on to the normal deposits forming on the sea-bottom, without disturb- 
ing them (see fig. 2, p. 293). 
(11) \ gently 
If, on the other hand, the float is stranded before it is entirely 
melted, it will do so gradually—scraping, at first gently, over the 
sea-floor, tearing up any slight obstacle, such as a coral or sponge, 
that may be attached or lying there and grinding smaller shells to 
powder. ‘The larger of the local materials will be carried forward 
with the stranded float; the smaller will be dealt with by the 
surrounding water. 
(12) Hence we ee expen ia find that nearest the shore are hummocka 
i ) 
hee mixed with the breccia-fragments, and 
bands of fine shell- or echinoderm-débris interstratified with the 
there forming 
of the period f[ - 
composed of larger { 
deposits { 
If, again, from the sea-floor an immovable boss of rock should 
project, and the float should impinge thereupon, it is very likely 
to squeeze up a little of the subjacent deposit. Hence 
(15) in the neighbourhood of a rock-mass of earlier date that part of the 
deposit which lies between the boss and the breccia { pe eit bent up 
into an anticlinal form. : 
The relations thus established between forces in action at one 
place and results observed in another, are exactly of the kind that 
have convinced us of the former presence of glaciers in this country, 
and they should carry the same conviction. 
VI. ConsIpERATION oF DIFFICULTIES. 
(1) The Occurrence of Plant-remains. 
The stems and leaves of cycads, the stems of conifers, and the 
fronds of ferns are said by Prof. Judd to occur in abundance ‘in 
the matrix of the brecciated beds.’ Such an occurrence, if the 
words are understood in what appears to me their most natural 
meaning, would be very difficult to account for on the theory of an 
ice-foot. A place that is covered with drifts of snow every autumn, 
which rest there all the winter, and carry down abundant fragments 
in early summer, is about the last place in the world in which to 
look for ferns and cycad-stems in a beautiful state of preservation. 
Further consideration, however, shows that there is a preliminary 
question which has no relation to any particular theory, namely, 
How could these things be carried uninjured, in whatever way 
Q.J.G.58. No. 230. ve 
