85. What is denudation? How do inclined strata prove that the strata have been denuded? How do faults afford proof of denudation? What have been the general effects produced by denudation on the face of the land?
86. What part have the subterranean forces acted in the formation of mountains? To what geological action is the present aspect of these mountains due? What has determined the direction of river valleys? How have the valleys, dells, &c. been formed? What effect have faults had in determining the direction of river valleys? What is supposed to be the origin of the deep rock-basins occupied by many fresh-water lakes? How is the waste of land by denudation compensated?
87. What are fossils? What is meant by petrifaction? In what kind of rocks do fossils occur most abundantly, and in the best state of preservation? and what reason can be given for this?
88. How do fossils afford proof of varied physical conditions? Give a reason for some rocks being more barren of fossils than others.
89. State some of the characters which distinguish broadly the older fossiliferous strata from those similar accumulations which are being formed in our own day.
90. How may we identify formations in separate districts? How is the interrupted and partial distribution of strata to be accounted for?
91. In what respect do the fossils in younger strata differ from those in older strata? What general proof can be adduced to shew that species have become gradually extinct?
92. Give an instance how fossils prove changes of climate in the past. What is supposed to be the cause of great cosmical changes of climate? Describe Mr Croll's theory of cosmical changes of climate.
93. What is the test of superposition? Mention another test of the relative age of strata.