86 Mr . Mills’s Objervations on 
paffed the entrance of Loch Tarbut, and obferved feveral 
Whyn Dykes, or lava veins, running into the fea. The 
Paps of Jura were moftiy covered by the fog ; but which 
breaking away at intervals gave us a view of their lofty fum- 
mits, and of the narrow ftripe of rock mentioned by Mr. Pen- 
nant (Voyage in 1772, p. 21 7.), called the Hide of the Old Hag, 
to which is annexed a curious legend ; but which, in reality, ap- 
pears to be the furface of a Whyn Dyke, running down the 
fide of the x cherty Mountain. After entering the found of Ilay, 
obferving a very confiderable Whyn Dyke, or vein of lava, on 
the Jura Ihore, we landed, and found it range N.'N.W. and S.S.E. 
It is of a dark colour and compad texture, and in fome parts will 
give fire with fteel. Near to this Whyn Dyke is a red argil- 
laceous fubftance, ftrongly impregnated with iron, and con- 
tained in an inclined ftratum, varying in thicknefs, and termi- 
nating in a cavern, whofe fides and roof are of the fame fub- 
ftance, but wonderfully broken and thrown into every direc- 
tion, as is the including chert, amongft which we found fome 
that is brecciated. 
Soon after we returned to our boat, a fquall of wind came 
on, attended with heavy rain, which almoft wholly obfcured 
each (hore, and continued till we landed at Freeport, wet and 
fatigued, but highly gratified by the recolledion of the many 
curious objeds we had vifited during our excurfion. 
It having been confidered as very extraordinary, that a bed 
of coal ftiould be found, as at Ardlun, incumbent upon, and 
furmounted by, a mafs of lava ; I was induced to look into 
fome of the authors who have treated of volcanic countries ; 
and find there are many inftances of coal in the vicinity of 
lavas, though I have not met with any precifely fituated like 
the coal at Ardlun. 
May 
