of Edinburgh , Session 1878-79. 
121 
lying on the surface, not only of red granite, but also of gneiss, 
quartzite, and limestone, none of which occur as rocks or strata in 
Staffa. 
About fifty yards from this place, a bank of consolidated shingle 
was observed, apparently an old sea beach about 36 feet above high 
water-mark, from the breaking up of which, in all probability, the 
boulders above specified were derived. 
Dr Macculloch, when he visited Staffa in 1818, noticed these 
boulders, and was much puzzled to account for them. He says — 
“ I must not quit Staffa without describing a bed of matter 
which, however foreign to the structure of the island, is by 
no means foreign to its mineral history, giving rise, at the same 
time, to geological questions of considerable importance. This is 
an alluvial deposit, consisting of various transported stones, which 
may be seen on the surface in different parts of the island. It is 
particularly conspicuous near the landing place, and on the western 
abrupt edge of the cliff. The fragments are of various kinds — 
quartz, granite, and blue schist, intermixed with blue quartz rock, 
and trap — all of them substances which enter into the composition 
of the neighbouring islands of Rum, Skye, and Mull, but which are 
found in situ no nearer than in the latter island. The distance of 
Staffa from Mull is not less than seven miles. The surface of the 
Earth everywhere presents appearances indicating great changes 
and revolutions, of which none are more unquestionable than the 
existence of transported stones and alluvial substances in countries 
far removed from those where similar rocks are now found in their 
natural situations. The insular position of the example now under 
consideration, proves that it could not have resulted from the flow 
of water, whether that flow was gradual or sudden, without at the 
same time supposing a state of the surface in which Staffa was 
continuous, at least, with the neighbouring island of Mull.” (Yol. 
ii. p. 22.) 
Macculloch here evidently alludes to the theory originally 
propounded by Sir James Hall for explaining the transport of 
boulders by a diluvial current. To render such a theory applicable 
to the Staffa boulders, Macculloch assumes the necessity of joining 
the island to Mull, though there are now seven miles of sea between 
them, with a depth of 50 to 60 fathoms. At that time, the idea 
