430 D. MACKINTOSH ON THE ERRATIC BLOCKS OF 
has been chiefly dispersed in much the same direction, the thickest 
part of both dispersions being in a direction about E.N.E. from the 
parent area. In the case of the Arenig dispersion the ground behind 
the parent area is lower than the area itself. In the Shap-fell dis- 
persion the reverse is the case; in other words, the average level of 
the ground behind the parent area is higher ; and this is also the case 
with the Eskdale area. The Criffel dispersing-area, like the Arenig, 
is backed by lower ground. In all these cases the ground in front 
is at the lowest level; and this may have had something to do with 
the direction of the dispersions. The central direction of the first 
stage of the Eskdale dispersion is 8.8.W.; after its reappearance on 
the south and east coast of the Irish sea, its central direction is 
between 8S. and §.8.E. The central direction of the first stage of 
the Criffel dispersion may be under the sea, and therefore cannot be 
ascertained. Southwards it runs 8.8.E. 
9. Extent of Area strewn with northern Boulders, and their general 
Mode of Occurrence.—Leaying the north, north-east, and east part of 
the Shap-fell dispersion and the Welsh part of the Arenig dispersion 
at present out of consideration, the extreme length of the great 
northern drift-area, from the Solway Frith to the neighbourhood of 
Bromsgrove (Worcestershire), is nearly 200 miles, and the extreme 
breadth, from the Forest Smithy (between Buxton and Macclesfield) 
to Beaumaris*, about 90 miles. Were all the boulders in this area 
to be disinterred without disturbing their positions horizontally, and 
were those which have been “ massacred,” or horizontally displaced, 
to be restored, and brought to their original sites, I believe they 
would show little preference for any particular form of ground, 
whether flat, low, elevated, rising, or fallmg. As they now exist 
they are often found on elevated ground; but it is probable that on 
low ground they are often concealed by the upper Boulder-clay 
which generally contains very few large boulders. They may often 
be seen at the bottoms of ravines, where they have been exposed by 
the brooks washing away the clay or sand in which they were im- 
bedded. They may likewise often be seen accumulated on the up- 
stream side of an eminence or pass; but as regards the latter they 
are more frequently to be found on the lee side, as if their inertia 
had carried them forward some distance after grounding. On the 
large scale the most noticeable fact connected with boulders is their 
tendency to accumulate near to the commencement or termination 
of their courses. Terminal concentrations may be readily explained 
by supposing successive accumulation behind (for the required time) 
granite blocks around Whasset and Milnethorpe, south of Kendal (Geol. Mag. 
for July 1871). It must have come from about N. 15° E., or, by way of Kendal, 
from Wasdale Crag, over ground at least 1300 feet above the present sea-level. 
Its direction is a little west of the opposite border of the dispersion, which runs 
north of Wasdale Crag, thus showing that the dispersion radiates over a little 
more than halfacircle. This radiation is not all continuous, however, excepting 
in the immediate neighbourhood of Wasdale Crag, the Milnethorpe branch 
being isolated. 
* T have not had an opportunity of tracing it further west than Beaumaris. 
