﻿1851.] 



FORBES ON THE OOLITES IN SKYE. 



109 



a different depth of water and under different circumstances ; a con- 

 clusion consistent with the indications presented by the fossiliferous 

 strata which it overlies and alters. 



Another view may be taken, however, of the origin of the basaltic 

 sheet intervening between the upper and middle oolites in Skye, one 

 which would seriously affect the preceding estimate of its date. It 

 may be regarded as intruded trap, insinuated between superior and 

 inferior strata at an epoch long posterior to that of the deposi- 

 tion of the former. A minuter investigation of the geological phee- 

 nomena of the north and west of Skye than has yet been made will 

 probably determine which view is the right one beyond question. 

 But in the present state of the evidence I incline to regard the basalt 

 as contemporaneous with the oolites, and as of the definite date which 

 its position in sequence of beds seems to indicate. The great spread 

 and uniform thickness presented by this sheet of basalt, as far as it 

 has been examined, the unaltered condition of the strata which lie 

 upon it, and the baking of the rocks beneath it and of those which the 

 jets connected with it pass through, are facts which determine me at 

 present to regard it as a bed of the date previously suggested. At 

 the same time, in the Loch Staffin section there are appearances 

 at some of the points where the trap bursts through the superin- 

 cumbent strata which I could not clearly make out, and which, from 

 their connection with the faulting of the beds, at first sight seemed to 

 indicate disturbances produced by the lower trap. My belief at 

 present is, however, that the disturbances alluded to are results of 

 the jets of amygdaloidal trap distinctly seen bursting through the 

 lower and middle oolites and the basalt, and breaking up and baking 

 the estuary beds and Oxford clay, on which the amygdaloid is over- 

 spread in mass. 



The area of the Hebrides appears to have been a scene of igneous 

 eruptions and disturbances of level from a very early geological period 

 down to the age of the newer tertiaries. These beautiful and sin- 

 gular islands present a rich field for geological explanation, much as 

 has been done among them. Their palaeontology, one of the freshest 

 and fullest mines for discovery yet remaining in the British Islands, 

 may be said to be unexamined. The working out of the exact rela- 

 tions in age of the igneous with the stratified rocks of the Hebrides, 

 and of the physical and vital phsenomena determined by the several 

 eruptions within their area will sooner or later be one of the most 

 delightful and best-rewarded tasks to which a competent observer 

 can apply. 



List of Fossils collected aX Loch Staffin, with Descriptions and 

 Figures of the New Species. 



Oxford Clay. 



Ammonites cordatus, Sowerby. 

 Ammonites Eugenii, Raspail. 



Ammonites Vernoni, Phillips ?, possibly a variety of A. hiplex. 



