60 Proceedings of Royal Society of Edinburgh. [sess. 
exhibiting the path of the tubes in longitudinal section, in which 
the annelid origin of the channel explains itself, as it seems to me, 
unmistakably to the eye. On showing it to an old fisherman at 
Inveraray, who knows the worms well as bait for his lines, and on 
asking him if he did not see the burrows there, his only reply was, 
“Oh aye, but that’s in the middle o’ the rock!” a difficulty which 
belongs to what the late Lord Derby called “ the pre-scientific 
age.” 
There is yet one other specimen to which I must refer, because it 
was one of those which for a time secured me as most like a 
vegetable impression. It consists in perfectly straight parallel lines, 
marked in black upon the white ground of the rock. The lines con- 
sist simply of black or dark bronze stains on the grains of the 
quartzite. That they represent the staining of annelid tubes I have 
now no doubt. It may be the result of that copious and almost 
ubiquitous deposit of the black oxide of manganese which Dr Murray 
has discovered on almost all organic matter long exposed to the pene- 
tration of sea- water. Or it may be due to an effect which is noted 
by Professor Mackintosh in respect to some species of these annelids, 
that where the animal dies in its tube it leaves upon the walls a 
black stain like a “a black carbonaceous film.”* 
I attach no importance whatever to any interpretation of these 
marks in the quartzite as regards the evidence they may thus afford 
against a notion which seems to have been lately started, that our 
western mica-slate rocks are not of sedimentary origin at all, or 
that their apparent bedding is not truly such, but is the effect of 
what is called foliation. No geologist, I venture to think, who has 
lived among these rocks as I have done, and who has become 
familiar with the innumerable proofs of sedimentary origin which 
they exhibit, can entertain this new notion even for a moment. 
The absence of organic remains in the presence of such obvious 
metamorphism affords no presumption whatever against their 
sedimentary origin. I have been accustomed sometimes to look at 
the enormous masses of secondary and tertiary limestones which 
constitute the maritime Alps in southern France, and to look in 
vain among these seemingly unaltered beds for the traces of shells 
or of other organisms. These, indeed, are found; but they are 
* Mackintosh, Mag. Nat. Hist., p. 7. 
