3& 



stratification may be studied to much advantage, as the whole measure is exhibi- 

 ted on the face of the mural escarpment, as it were, in miniature — none of the 

 usual series being wanting. 



Across Brodich Bay the mountains exhibit a very dift'erent but less imposing 

 aspect ; and, instead of the serrated outUnes we have just observed, they are seen 

 rising in steps or stairs, and convey the best possible idea of the trap formations. 

 They are composed mainly of phorphyry and greenstone. A fine-grained granite 

 is also found here, and was first discovered by Mr. Ramsey, in 1837, and is hp- 

 lieved to be the very newest of the kind yet known. The reasons assigned by 

 Mr. Ramsey for believing it to be the newest are, that no fragments of it are found 

 in the neighboring rocks. It often sends veins into the slate, but, when raised to its 

 present elevation, it could not have been in a state of fusion, from its being never 

 found overlying the slate, which has evidently been fissured and partly elevated be- 

 fore the deposition of the old red sandstone. It is also found penetrating the 

 coarse granite, which is also traversed by dykes of porphyry and greenstone, while 

 the fine granite is never thus penetrated ; and indeed there is reason to believe that 

 it is newer even than the traps with which it is found, and it also sends veins into 

 the new red sandstone, which conclusively establishes its recent origin. The 

 slates in its vicinity exhibit evidences of the action of fire, having been partially 

 fused and the strata greatly disturbed. Sometimes they assume a granular ap- 

 pearance similar to the true igneous intrusive rocks. 



Sailing south of Brodich Bay, some very beautiful and well defined dykes of 

 greenstone are seen, and also a remarkable pitchstone stratum, about 14 feet thick, 

 which has been intruded horizontally between the old and the new sandstone. 



The great importance oi fossil remains, es^eciaWy oi fossil ichthyology, to 

 identify formations locally remote from each other, was frequently insisted on by 

 Mr. Murchison in the course of the day, and it seems to be a favorite proposition 

 of his, to which I shall have occasion to refer hereafter. 



The scenery in the vicinity of Brodich Bay and "Holy Island" (which is form- 

 ed of trap resting on new red sandstone) is said to be not inferior to any other 

 views in the highlands of Scotland, and repeatedly during the excursion called 

 tbrth spontaneous exclamations of admiration from the party, as some new beauty 

 ia glen or mountain was discovered. 



At three o'clock we landed at Brodich Castle, under salutes of cannon from the 

 «hore and from the steamboats at anchor. At the wharf we were joined by Mon- 

 liieur Agassiz, who had reached the island by some other conveyance. On land- 

 ing, we were received by the Marquis of Douglass, as the "representative of his 

 father, the Duke of Hamilton, and were then marched up to the Castle, with the 

 hereditary piper in full costume at our head, playing the Gathering of his Clan. 

 At the Castle we sat down to a sumptuous entertainment, prepared by the Mar- 

 quis for the refreshment of the company. During the repast many toasts were 

 drunk, and several good speeches delivered. Among the best speakers was Dr. 

 BvcKLAMu, who is a great gun, being Canon of Christ Church, Oxford. 



We left Brodich at six o'clock, on our return to Glasgow — every one apparent- 



