398 Proceedings of the Royal Physical Society. 
all the other localities mentioned, in the hard clay itself. 
The Burn of Strath, to beyond the "Crowners Garden/' is 
equally rich in clay and organisms. In one very small spot 
beyond the last-named place, I got many nice specimens of 
Melohesia, some of them very little rubbed. Can this be an 
old sea bottom ? I regret that I was never able to get there 
again when the river was low, to work this out. The Burn 
of Watten deserves a good search. The high cliffs over 
Scrabster are thickly capped with clay, and the upper face 
of the rock on which it rests is smoothly polished and deeply 
grooved ; such is the case with the whole of the rocks on 
which the clay is deposited. Hence to Thurso, and all along 
the river to far inland, the clay is abundant. At " Geize," 
old John Busby, in 1802, " found blue clay-marl in great 
plenty intermixed with marine shells," and also at Dale- 
more. What a pity it is that this interesting discovery was 
lost sight of so long ! 
From Thurso, all along the side of the Pentland Firth to 
Mey Castle, Canisbay, John o' Groats, Duncansbay Head, 
thence to the Burn of Freswick, Keiss, and to Wick, thence 
to Lybster, Forse, Latheron, Latheron Wheel, Dunbeath, 
&c., in all these places, and many more localities, I have 
found organisms in greater or less quantities. Although 
the clay is not uniform in texture, being finer or coarser, in 
some places almost free from stones, and these of small size, 
in others — even at short distances apart — it is full of stones, 
many of large size, and in all places polished and grooved 
ones are far from rare. The clay itself is always hard and 
rough to the touch. For the present, although considered 
objectionable by many, it will be well to retain the name of 
boulder clay for the deposit. I do not object to its being 
called glacial, for it evidently was in the first instance 
derived from, glaciers, but forced to sea and deposited by 
icebergs stranded on the Caithness shores. These icebergs, 
when first launched into the sea by the ice-streams from 
the glaciers, picked up some of the sea-bottom, with its 
organisms ; and when on their voyages, wherever they 
touched, they added to their burthen by picking up more 
