267 
of Edinburgh, Session 1878-79. 
the boulder lay, had an excavation made in the boulder-clay, along 
the south side of the boulder, to see if there were striae on it also. 
It turned out that there were. 
I found that on the north side of the boulder the striae ran in a 
direction from W.S.W., and on the south side from N.N.W. 
The annexed diagram (fig. 4) represents this boulder, with its 
north and south sides striated at the west end of the boulder. The 
striae were rather more numerous on the north side, AB, than on 
the south side, CD. 
Evidently it was the same agency which produced the striae on 
both sides. By coming against the boulder at its west end, this 
agency, whatever it was, had separated into two streams or coulees , 
and had marked both sides, by pressing upon them as it passed. 
Fig. 4. — Drylaw Boulder, near Linton. 
Now this could have been effected only by a body coming from 
a direction intermediate between N.N.W. and W.S.W., i.c., 
about W.N.W. The agent which thus divided into two streams 
must have consisted, not of an inflexible solid body, but of “a 
mass,” as Mr Stevenson calls it, capable of separation. The clay in 
which the boulder was buried was a body of this character. It con- 
tained numbers of pebbles, as usual in boulder-clay, some so hard as 
with pressure to be capable of smoothing and scratching any rock 
against which they were pressed. Sir Thomas Hepburn showed to me 
aportion of a small granite boulder which he had picked out of the clay. 
