OF THE TRAP-ROCKS OF SCOTLAND. 649 
Oxford Clay. To the age of these syenites must be attributed the remarkable 
metamorphism of the Lias Limestone of Strath,* and possibly also that of the 
hypersthene of the Cuchullin Hills. 
It is not, however, until we pass up into the upper part of the Lower Oolite 
that we meet with continuous sheets of greenstone. These, often beautifully 
columnar, are found resting on the precipitous line of cliffs north of Portree, and 
capping the higher part of the opposite island of Raasay. In their lower portion 
they appear intruded among the limestones, shales, and sandstones; but as we 
trace them across the north-western part of Skye, they are seen to be regularly 
interbedded among estuary limestones and shales. The deep indentations along 
the northern shore of the island are due to the wasting away of these strata ; 
while between the lochs the sheets of greenstone swell into rugged heathy hills, 
or shoot up as precipitous cliffs, which the frosts of winter are carving out into 
grotesque pillars, and wearing down into heaps of rubbish. 
Fig. 2.—Diagram-section to show the intercalation of Igneous Rocks among the 
Oolitic Strata of Skye and Raasay. 
Skye. Sound of Raasay. Raasay. 

The estuary beds of Loch Staffin, worked out by Edward Forbes in 1851, form 
the lowest of the group, and are succeeded by enormous sheets of greenstone 
and basalt (g, fig. 2), between which occur other estuary limestones and shales, 
along with several seams of coal (0). During part of the autumn of 1858, I ascer- 
tained this to be the structure of the wide sweep of country, hitherto coloured as 
one sheet of trap, extending from the Atlantic to the Sound of Raasay, but I was 
prevented from working out the details. It is not one sheet of greenstone, but a 
series of successive sheets, with fossiliferous bands between. The fossils collected 
by me from these bands are now in the hands of Dr Wright, who has kindly 
undertaken their examination. 
- That these greenstone beds are contemporaneous with the strata among 
which they occur I have little doubt, though another visit will be needed before 
this statement can be fully verified. Their mere extent and regularity, as well 
as the unaltered character of the shales, limestones, and coal beds, wherever I 
have seen them, seem indications of synchronism rather than intrusion, an 
opinion that was very strongly maintained by Dr Bou£.+ 
* Quart. Jour. Geol. Soc., vol. xiv. p. 1, et seg. 
+ Essai Geologique sur l’Ecosse, p. 220, et seq. 
VOL. XXII. PART III. 8F 
