Vol. 67.] ANNIVEBSARY ADDEESS OF THE PRESIDENT. lxXXVU 



Lancashire and Cheshire Coalfield which appears to point in the 

 same direction. 



I think that we may conclude from this example, which is typical 

 of many, that cases of recurrence in our cycles of deposition are not 

 likely to occur with frequency or exactness ; but that under the 

 complexity of causes which operate to impart to the strata their 

 dominant characters there will probably be eases of reinforcement 

 or interference which will give to each cycle, and each phase of a 

 cycle, its individual characteristics. 



Although in Britain we have cause to be grateful for a System 

 like our Carboniferous, which provides us with so wide a range 

 of products of economic value, we must acknowledge that our 

 country has but an insignificant place in a table showing the world's 

 distribution of native petroleum. But when we pass into the chief 

 regions where petroleum is obtained, we must be struck by the 

 restriction in its distribution. The problem of that distribution 

 is complicated by the fact that, while coal remains stationary in 

 the beds among which it was formed, petroleum can migrate, like 

 water, from one formation to another ; and the beds in which it is 

 now stored may be separated considerably from those in which 

 it originated. Even then, however, it tends to occur in rocks of 

 rather restricted range. The constant association of petroleum, 

 when indigenous in the rocks in which it now occurs, with the 

 anomalous deposits which we associate with inland lakes and 

 closed continental areas, gives a strong suggestion that the origin of 

 petroleum is to be sought, not so much in special chemical reactions 

 influencing chance organisms that may be preserved in rocks, as 

 in a concurrence of the several special geographical conditions 

 regulating the nature of the deposition and the existence and pre- 

 servation of life-forms at certain phases of earth-history. 



(9) Other Effects of Earth-Movement. 



The intensity of the results of the successive movements gives 

 the impression that it is related to their antiquity ; but it is 

 certain that intensity is, in reality, related to the distance of any 

 part affected from the main focus of action. The folding, thrusting, 

 and cleavage of the Charnian rocks and the disturbance and 

 cleavage of those of the Longmynd appear to have been effected in 

 pre-Cambrian times. In the latter case, the ring of Cambrian^and 

 later sediments remains unaffected by cleavage. 



The more severe effects of the movements with Caledonian trend 



