m 
TilE GEOLOGIST. 
beneath us as having been subjected to many vicissitudes, and to frequent 
and more or less vast and important fluctuations of level ; that, some- 
times above the waters, it has been clothed with vegetation and with 
appropriate forms of animal life, and sometimes beneath the waves, 
fresh sediments, enclosing the creatures of the deep, have covered the 
terrestrial conditions that were ; and then again uplifted, the new 
deposits have been covered with verdure, and fresh forms of living 
creatures have appeared, 
A glance at the section (p. 93) will show that, for the purpose for which, 
at my request, my talented and highly- valued friend, Mr. T. Rupert 
Jones, designed it in connection with these papers, it is necessary 
only there to indicate the great disturbances which affected our own area 
during the Silarian period, and those other great disturbances by 
which the Palteozoic period was terminated and cut off from the 
Secondary or Mesozoic period, which succeeded it. In the grand se- 
quence of events there displayed, we have, first, the gneiss and "bottom 
rocks" upheaved ; then a sinking of the land for ages, with accumula- 
tions of sediments j a counter-upheaval of a largo tract, with a general 
denudation of the surface followed by a continued gradual subsidence of 
the whole, with more and more deposits, continued up to the period when 
the sediments had well filled up extensive portions of the ancient 
sea-bed, forming low banks and islands, and a;stuarine and land-lock 
coasts, on and around which the gigantic vegetation, which the warm 
and humid atmosphere nourished and fostered, grew in wild luxu- 
riance, and, mingling with the drifted trees and plants brought by 
the rivers and currents to the tranquil bays, formed part of that 
great accumulation of vegetable matter which has been since, by 
the chemistry of nature, elaborated into that wonderful and invalu- 
able mineral, coal. After the deposition of the coal-measures, 
something like the ancient conditions returned; the new red sandstone 
formation spreading out above them, so like the old red sandstone 
aeries beneath in its marls and conglomerates, that only by position 
and by the difference of the creations each has entombed, can the one 
be distinguished from the other. "With the Permian catastrophes 
our share in the first world ended. But these catastrophes were not 
universal. The disturbances which have made the line of demarcation 
between the primary and secondary groups of rocks so strong in our 
own island, were limited in their area and iu their clfucta. In other 
