of Edinburgh, Session 1878-79. 
191 
travelled many miles; for there is no greenstone of the kind in the 
hills, and none near them, except in situations 500 or 600 feet 
lower. 
This block has probably been transported in the same manner as 
the mass of mica slate (a above). 
e. The same remarks apply to a greenstone boulder lying half a 
mile NiW. of Logan House, on the south side of West Black Hill, 
about 1400 feet above the sea. It is of 12 or 14 tons weight. (See 
plan, M. 5.) 
There are many others in elevated situations of 3 or 4 tons 
weight. 
The substance is generally greenstone, the least brittle probably 
of all rocks, and of course the best fitted to resist fracture. Nearly 
all the blocks have their angles rounded off. 
/. On the banks of Eight Mile Burn, in the low ground, there is 
a mass of alluvium about 100 feet thick, containing hundreds of 
trap boulders of all sizes up to 10 tons weight. It consists of two 
beds, — the older, a blue unctuous clay, the newer a red clay. The 
large blocks are chiefly in the latter. 
There are many similar travelled blocks in the bum flowing from 
the old Beservoir to Bonally, and probably in all the streams of 
these hills (page 303). 
2, Professor Geikie, in his Memoir “ On the Geology of the Neigh- 
bourhood of Edinburgh,” published in 1861, observes (1) that 
“ boulder-clay lies along the north-west flanks of the Pentlands, 
rising to a level of at least 1300 feet.” 
When the clay has been recently removed, we usually find the 
rock below polished, grooved, and scratched in a direction nearly 
E. and W., or E.S.E. and W.N.W. These markings even remain 
distinct on hard greenstones which have remained exposed to the 
weather for an indefinite period. 
The parallelism of the striations throughout the present district 
shows that the floating ice must have moved in a pretty uniform direc- 
tion; and that it was from the west is rendered clear by the striation 
of the western face of the hills, by the great depth of drift on their 
eastern sides, and by the fact that the transported boulders, when 
traceable to their parent rock, have been carried from west to east 
(page 126). 
VOL x. 
x 
