HUM. GEOLOGY. 489 



position, the thin and numerous beds of the augit rock 

 passing into the massive syenite by imperceptible degrees. 

 I have given to this rock the name of syenite on account 

 of its general resemblance to the syenites which in similar 

 circumstances are associated with the ordinary traps, and 

 because there is at present no term by which it can be 

 designated. It ought however to be distinguished by an 

 appropriate name, since the ingredient united to the felspar 

 is, in this case, augit, and not hornblende. But this is 

 only one of many desiderata in the arrangement of the 

 trap rocks, and I shall hereafter take an opportunity of 

 examining this part of the subject in one collective point 

 of view. 



From the facts now stated, some general conclusions 

 may be drawn that are of importance in the history of 

 this family. The first of these relates to the imperceptible 

 transition from the massive and amorphous to the lami- 

 nated or stratified structure ; and it may perhaps throw 

 light on some obscure points respecting those trap rocks 

 which appear to be regularly stratified. As far as relates 

 to those that alternate with the common stratified rocks, 

 there is nothing to add to the remarks deduced or de- 

 ducible from the phenomena described in Sky and in Egg. 

 But in many instances an apparently stratified disposition 

 exists in them where no such alternation takes place ; an 

 example of which will be found in the account of Bute. 

 These are illustrated by the present case, and are probably 

 equally independent of a real stratification ; using that 

 term in its most proper sense, as the result of a deposition 

 either from solution or suspension in a fluid. It is easy 

 to conceive how an amorphous mass may in certain cases 

 put on the semblance of stratification, but it is not so 

 easy to imagine that a substance deposited by either of 

 the processes above mentioned should in one place be 

 regularly disposed in thin beds, while in a neighbouring 

 and continuous portion it should form irregular mountain 

 masses like those of the island under review. As the 



