512 British Association Reports. 



Now in distarbed districts, and in many not much disturbed, faults 

 are more or less numerous, and they are of all ages and of varying 

 amounts. On the continent of Eiurope and in Britain, for example, 

 from the Middle Tertiary strata downwards, somewhere or other, all 

 the formations have been dislocated, some of the faults being of the 

 amount of only a few inches or yards, and others of many thousands 

 of feet. Several I know in Wales of 2,000, 5,000, or even 12,000 

 feet in amount ; and as a rule it is found that the greatest faults, 

 intersect strata that have been most disturbed, while also it often 

 happens (but not always) that the oldest strata have undergone most 

 disturbance, because they have been more frequently affected by 

 disturbing agents. On the north side of the Alps the Miocene rocks 

 of the Ehigi are inverted and faulted against the older formations, 

 and the amount of the throw must be very large, and as many 

 Miocene species of molluscs are still living, far as it is removed from 

 our epoch, this fault, by comparison with older ones, may almost be 

 said to approach our own day. 



Now the question arises whether the agencies that produced con- 

 tortion of strata and faults, which in certain cases have resulted in 

 the formation of great mountain chains, have been sudden in their 

 operation, or if the changes have been as progressive and gradual as 

 the operation of those agents of denudation — the sea in the formation 

 of plains of marine denudation, old and new, and the outlines of 

 coasts, and the work of air, rain, rivers, frost, snow, and ice, that, 

 long continued, have produced the familiar sculpturing of hill and 

 valley. This is a veiy pvizzling question to geologists, and various 

 opinions have been stated. One of these is that we now live in a 

 world, as it were, nearly in a finished state, and which will suffer no 

 more catastrophes ; another that the world now remains in a tempo- 

 rary state of repose after a succession of spasmodic throws which 

 broke up sudderdy great portions of the earth's crust, and repeatedly 

 revolutionised the world, and that such efforts may reciu: at later 

 periods a long way beyond our time ; or again, that the state of 

 tranquillity we now enjoy, in which change is constant, more or less 

 slow, and very sure, has been the order for all time, as far as 

 geologists can trace back the history of the world in the rocks that 

 form its crust. These are the leading opinions on the subject, and 

 my own inclines to the last. 



But in the present state of our knowledge it is impossible to 

 reduce to a demonstration the truth of this opinion. Those who 

 fancy the world to be in a finished state, are forgetful of the fact 

 that the old rocks were made by the same ojperations as the rocks 

 that are now forming, and those who advocate siidden violence and 

 wide-spread revolution have, it seems to me, nothing beyond asser- 

 tion to help them, founded on that kind of wonder and awe that 

 arises from the contemplation of crags, peaks, and the invertions of 

 the strata of great mountain chains, or of other and kindred pheno- 

 mena ; while the advocates of peaceful change have little to say 

 beyond an appeal to observed facts, gathered from a study of rocky 

 masses and their contents, that to them seem to point throughout to 



