Chap. XX.] 
PKOOFS OF SUDDEN CHANGES. 
495 
sible extension of gradual and insensible causes could huge masses of Ter- 
tiary rocks have been so thrown over as to pass under the older rocks of 
the Alps, out of which they were formed. That operation must have been 
paroxysmal, and no slow process could have accomplished it. The crust 
and outline of the earth are, in short, full of evidences that many of the 
ruptures and overthrows of the strata, as well as great denudations, could 
not even in millions of years have been produced by agencies like those of 
our times. Nor can I admit that we who appeal to the proofs of former 
intensity of causation are to be taxed with being ' prodigal of violence and 
parsimonious of time ; ' for we willingly allow any amount of time for the 
accretion in aqueous sediments of such matter as resulted from the diurnal 
wearing away of lands. We also readily admit, if valid proofs be given, 
that gradual uprisings and sinkings of lands have occurred in parts of the 
earth during the historic period ; but, at the same time, we maintain that 
formerly acts of much greater violence in the dismemberment, and in de- 
nudation, of the strata took place than in any changes during our era. 
Fully admitting that " deposition and denudation are processes insepa- 
rably connected"*, it is immaterial to my argument whether the destruction 
of vast masses of matter was both sudden and gradual or gradual only ; for 
the amount of deposition would in all such cases balance the amount of 
abrasion ; and whether the hills were ground down gradually or suddenly, 
the resulting detritus accumulated under water would be the same. If, 
indeed, it be rational to infer that, by the progressive thickening of the 
sedimentary crust, the internal heat being more and more repressed by each 
such addition, the surface has at length been fitted for the habitation of an 
intellectual being, are we not naturally led to believe that in historic times 
the earth's surface has been in a state of comparative repose, and subject 
to much more moderate undulations and depressions only, though here 
and there materially diversified by earthquakes and volcanic outbursts ? 
Again, I can see in existing nature no cause of sufficient intensity to 
account for ordinary sediments (once charged with organic remains) having 
been changed into crystalline masses occupying whole regions. The theorist 
in vain endeavours to explain such operation by processes so slow in their 
action as to be almost imperceptible. If it be argued that the strata con- 
stituting lofty mountains were metamorphosed in parts by such a slow 
process, let any one who sustains that view explain how it is that every 
stratum in a lofty range of mountains, composed of carbonate of lime, 
should in some cases all at once change into sulphate of lime, and in others 
into dolomite. 
Whilst I state my objections to some of the tenets held by a large band 
of modern geologists, I am bound to say that I rejoice to witness the can- 
dour with which their eminent leader, Lyell, has recently written of de- 
posits formed after what he terms " great revolutions in physical geo- 
* See Lyell, 'Principles,' 10th edit. p. 107. 
