o f Edinburgh , Session 1878 - 79 . 
187 
large slab of sandstone lying in the gorge of the Bonally Burn, 
derived from beds of the same rock about half a mile to the S.W. 
In a deep cutting recently made in the boulder clay at Aln- 
wick Hill, near Liberton, I observed many boulders of Old Bed 
Sandstone, which must have been carried from the vicinity of the 
Carlops, where the same rock occurs in situ. There were also 
boulders of various varieties of porphyrites, which form the hills 
to the S.W. The same remarks hold good with regard to boulders 
I saw dug from very deep excavations made two years ago at Sea- 
field, near Leith, all bearing out a transport of some kind along the 
trend of the Pentlands, or from S.W. to N.E. 
A fact in connection with the Old Bed Sandstone boulders I ob- 
served at Alnwick Hill appears worth recording. Many of these 
boulders were very round and smooth, so much so that they sug- 
gested the idea that the agent which transported them to their pre- 
sent position could not have produced this effect during transport, as 
the distance from their source is so very small, but in all likelihood 
found them worn and rounded before being carried along. 
NOTE ON THE BOULDER CLAY. 
There is, in my opinion, no true till or boulder clay resting on 
any of the Pentland summits. What has been described as such 
by Dr Croll on the top of Allermuir Hill seemed to me simply a 
peaty soil formed by the decomposition of the underlying rock and 
debris, and the decay of vegetable matter, making up a heterogeneous 
deposit which, however, has no connection with the true boulder- 
clay occurring at lower levels. 
II. 
Notes on Drift and Glacial Phenomena on the Pentland Hills. 
By John Henderson, Curator of the Phrenological 
Museum, Edinburgh. 
The following phenomena were noted by me during a number of 
visits I made to the Pentland Hills ; but as my chief object then 
was to examine the older rocks, my observation on the recent 
deposits are by no means complete. 
