Why do subsidences occasionally follow these movements of elevation? Mention instances. [Illustration: Fig. 82.] What explanation is suggested of deep and extensive chasms? What conditions must exist together, in the force by which continents are produced? What cause fulfils these conditions? What is the proof that the temperature under given localities is variable? What will be the result of these variations? What is the law of expansion of rocks, as obtained by experiment? What amount of change of level may be thus accounted for? What circumstances would probably increase this amount? What amount of vertical movement must be accounted for? Why must these changes of level be very slow? Under what conditions would there be no change of level? Is it probable that these conditions exist to any great extent? Why, then, are not the changes of level observed? Why is the bed of the sea most likely to experience the change of elevation? Why are the continents most favorably situated to undergo depression? What are the sources of heat upon which climate depends? Does the interior temperature sensibly affect the present climates? What cause may be assigned for the changes of climate which are known to have taken place? What are the relations of land by which the highest temperature would be produced? How would this distribution of land affect the temperature of the waters of the ocean? What would result if the opposite relations of land and water existed? What confirmation of these conclusions is drawn from the existing climates of different parts of the earth? Is there any reason to suppose that the relations of land and water which would have produced a warmer climate in former times did not exist? End of the Project Gutenberg EBook of The Elements of Geology; Adapted to the Use of Schools and Colleges, by Justin R. Loomis