50 Dr. C. Ricketts—Changes in the Earth’s Crust. 
Excepting by very few it was formerly assumed that the 
sculpturing of mountains, and the formation of valleys, etc., were 
due to the action of the sea. Again, that ‘‘ the excavation of valleys 
could be ascribed to no other cause than a great flood of water, 
which overtopped the hills from whose summits these valleys 
descend.” It has been considered “they are due to cracks, rents 
and gorges of fissure in the rock-masses, in some of which rivers 
flow ; that these fissures have been caused by upheaval, by ruptures, 
and denudation,” and “that mountain valleys lie in lines of cur- 
vature, dislocation and fracture.” No endeavour was made to 
demonstrate how any of these various causes could have excavated 
valleys, and it is very remarkable that there was no attempt to 
account for the redistribution of the materials which had been 
removed. It is probable that the difficulty of making the present 
conformation of the Harth’s surface coincide with a preconceived 
chronology, may have had great influence in the formation of such 
opinions, even by those who are justly considered fathers in 
geological science. We are constantly reminded how greatly this 
feeling is impressed on the popular mind in expressions made by 
persons unacquainted with geological science; with those who may 
be considered educated, ‘“‘I presume it is antediluvian ;” with the 
workman or labourer, “It was there afore th’ flood!” Walking 
through one of the minor gorges in the Carboniferous Limestone of 
North Derbyshire, and conversing with an intelligent man native to 
the district; on the remark being made, that some persons think 
these dales have been formed by the streams that run through 
them, the immediate and emphatic reply was, ‘No! that could 
never be;” and, pointing to the rivulet, ‘Why there is not water 
enough to drown a mouse. You may depend upon it all these 
places were cut out when the world was drowned.” 
Hutton (1795) and Playfair (1802) demonstrated that the for- 
mation of valleys was due to the effects of atmospheric agencies. 
Playfair says, ‘“‘ Water in every state from transparent vapour to 
solid ice, from the smallest rill to the greatest river, attacks what- 
ever has emerged above the level of the sea, and labours incessantly 
to restore it to the deep. The parts loosened and disengaged by the 
physical agents are carried down by the rains, and, in their descent, 
rub and grind the superficies of other bodies ; and, when rain descends 
in torrents, carrying with it sand, gravel, and fragments of rock, it 
may be truly said to turn the forces of the mineral kingdom against 
-itself. Every separation which it makes is necessarily permanent, 
and the parts once detached can never be united save at the bottom 
of the ocean.”! ‘All river channels have been cut by the waters 
themselves ; they have been slowly dug out by the washing and . 
erosion of the land.’’? 
A long time elapsed before this explanation was accepted, not until 
there occurred in the early volumes of the GroLtocicaL MaGazINE 
a prolonged discussion on the subject, which proved that a great 
1 Playfair's Illustrations, etc., § 95, p. 111. 
2 Tllustrations, § 99, p. 114. 
