Mineralogy of Sky. 55 



occupying the great mass of the island, from the difference of their 

 external characters and form, and from the existence of some par-^ 

 ticular varieties in the one, which are not found in the other : but 

 I have not the means of drawing this distinction, nor of saying 

 where or how they are connected or disjoined, I have little doubt 

 that there are distinct deposits of trap rock of different periods, 

 as well as that there are veins of the same ; but whether these 

 two leading divisions in the external appearance of Sky are also 

 distinctions in the geological aera of the rocks which form them, 

 is more than I can determine, since they have no distinct set of 

 connections by which such a supposition could be verified. Further, 

 when I attempt to trace their connection with each other, I ima- 

 gine that I can every where see the mountain trap of the Cuchul- 

 lin, blending with the stratified trap of the coast ; and this opinion 

 is confirmed by every thing which I have observed in Mull, where 

 every possible variety of this rock from Gribon to Ben More, and 

 thence to Loch Don on one hand, and Mornish on the other, ap- 

 pear to succeed each other without discontinuity or interruption, 

 and with changes of character so gradual, that no line of interrup- 

 tion can any where be found. As however I consider this to be an 

 object of the first importance in the history of this rock, I shall 

 still suspend my judgment, pointing it out to other geologists as a 

 subject highly worthy of investigation. 



As I consider the term foetz to be in this case improper, since it 

 implies the hypothesis from which it is borrowed, I have distinguished 

 that trap which is placed in a horizontal form, and of which the 

 terraced edges are so very characteristic, by the name of stratified 

 trap, using the term beds or strata indifferently, and without 

 meaning by the use of either to insinuate any thingres pecting 



