5 4 Mr. Mills’s Gbfer*uatwns on 
Bull Sound. On the (bore are pebbles of bafaltes, of granite, 
and of gneifs ; and from the firm rocks we collected feveral 
fpecimens of granite, in which the feldfpath, quartz, and 
black mica, are differently blended, but without any (hoerl. 
During our flay at hidden, I learned from Mr. Stewart^ 
that Rhos Mull, which is the N.W. part of Mull, is chiefly 
red granite: in the fouthern part of the ifland is very fine- 
white freeftone, and between that and the granite ail whyn- 
ftone. The ifland of Lifmore, in the found of Mull, is in- 
tirely limeftone, excepting where it is croffed by the Whyn 
Dykes. In the ifland of Uiva are pillars fomewhat refembling 
thofe of Staffa, but of a paler colour. — Canna alfo is bafaltic, 
and refembles Staffa, — The Dutchman’s Cap has rude pillars - — 
Cairuborough the fame. Dunvegan in the ifle of Skye has 
bafaltic pillars, fimilar to Staffa. — On the fouth-weft fide of 
the ifle of Egg is a curious cavern. 
We again embarked for Hay ; but, it being calm, and the tide 
againft us, were obliged to anchor ; and we landed on an ifland 
which forms the S.E< point of the found of Iona. From the 
point, which is a bare rock of red granite, broken and jointed 
in every direction, I obferved the following bearings. Icolm- 
kilm Church N.N.E. — The northernmoff part of Stafia, over 
the N.K. point of the found of Iona, N.E. by N. — The fouth 
Pap of Jura, over Colonfay, S. 
The upper furface of the granite, even in the very higheft 
part, is all convex, which feems to prove, that by fome con- 
vulfion it has been thrown up from the bed of the ocean* 
which, by long wafhing over it, had previoufly worn down its 
fiibftance at the edges of all its numerous joints. On the eaft 
fide of the point, and on the weft fide of a little bay, where 
the granite cliffs are at leaft fifteen yards perpendicular, we 
i . difcovered 
