R. M. Deeley—Traul and Underplight. 3 
was called Trail and Underplight by Spurrel.' It would appear that 
many of the disturbances which have been produced in drift and 
- other deposits by the passage of ice over them are not of the same nature 
as those which occur in Underplight. Boulder-clays, for example, 
are often kneaded into the soft rocks upon which they rest, and thick 
deposits of sand and gravel have been disturbed greatly by ice which 
has passed over or been pressed into them. Disturbances of this 
nature have been described by Boswell? as occurring in the Suffolk 
Valleys. They affect Chalk, Thanet Beds, Reading Beds, London 
Clay, Crag, and glacial beds alike. In this area the trend of the 
summits and troughs of the folds, and other phenomena, indicate 
that the contorting force acted down the valleys, and the features noted 
are such as could not be produced by slip down the valley sides. 
I have described and figured * the nature of the disturbances in the 
gravels, sands, ete., of the Trent Basin, which, from the strike of the 
ridges and troughs, show that they were due, like those described by 
Boswell, to forces acting down the main valleys. Such disturbances 
often present some of the features shown by Trail and Underplight, 
but, although this is the case, they do not appear to be of this nature. 
Fie. 1.—T, Trail; UP, Underplight. 
Osmond Fisher‘ noted the surface feature we are considering very 
carefully ; but was of opinion that the phenomena resulted from the 
infilling of drainage channels with rainwash and stones, combined 
with flow of the surface deposits. Such infilled channels certainly 
occur, and may be seen in the brickearth pits at Erith ; but whether 
they are washouts produced by floods or prehistoric infilled game pits 
it is not always easy to make out. 
In the paper already mentioned Spurrel deals with the question 
of the formation and nature of Trail and Underplight in some detail. 
According to him a typical section shows (1) vegetable soil, (2) rain 
warp, (3) Trail, and (4) Underplight. The vegetable soil is to 
a large extent the result of the activity of earth-worms as described 
by Charles Darwin. The rain warp, an unstratified more or less 
sandy clay with pebbles, varies in thickness from a few inches to 
several feet. The Trail generally consists of a more or less sandy 
clay with pebbles, and fills the troughs in the Underplight. The 
Underplight is the soft rock on which the Trail rests, and has been 
contorted so as to form irregular pits or troughs in which the Trail 
1 A Sketch of the History of the Rivers and Denudation of West Kent, etc. 
2 Q.J.G.S., vol. lxix, pp. 581-618, 1913. 
3 Thid., vol. xlvi, pp. 437-79, 1886. 
4 Thid., vol. xxii, pp. 553-65, 1866. 
