Why are not fossils distributed uniformly through all the formations, and through all the parts of each formation? In what does the importance of fossils consist? How are the fresh-water and marine formations distinguished? What circumstances render it difficult to identify rocks of the same age in different localities? How are formations identified? Was the work of creation one of short duration? What was the last work of creation of which we have any geological evidence? Why may we presume that no more species will be created? Do all the animal and vegetable species which have been created still exist? [Illustration: Fig. 44.] [Illustration: Fig. 45.] [Illustration: Fig. 46.] [Illustration: Fig. 47.] What causes are operating to destroy species? SECTION VII. How long has it been since the creation of the earth? How does the amount of stratified rock indicate the great antiquity of the earth? How does the stratification show the same thing? What is the proof that the principal strata were deposited before the creation of man, and how does this fact bear upon the question of the antiquity of the earth? Give the argument drawn from the successive creations and disappearance of animal and vegetable species. The argument drawn from the amount of organic matter in the stratified rocks. The argument from slow accumulation. What is the general conclusion from these facts? Why is this conclusion an important one? What objection to it has been raised? How is this objection answered? What additional explanation is given? CHAPTER III. SECTION I. What is the deepest geological change of which we have any knowledge? What are the reasons for supposing that the lowest stratified rocks are undergoing fusion? Why are the lowest stratified rocks regarded as of mechanical origin? What changes have they undergone? SECTION II. In what state were the stratified rocks deposited? What change have they undergone in this respect? How is the fissile structure produced? How is the cleavage structure produced? [Illustration: Fig. 48.] What is the third class of changes? What do fractures at the surface become by the erosion of water? How are caverns formed? Describe a vein of segregation. A dike. A mineral vein. What is a fault? Were the inclined strata thus deposited? How is it proved that they have taken the inclined position since they were deposited? What is the direction of the dip? What lines form the angle of inclination? What is the outcrop of inclined strata? The strike? [Illustration: Fig. 49.] [Illustration: Fig. 50.] [Illustration: Fig. 51.] [Illustration: Fig. 52.] [Illustration: Fig. 53.] Describe an anticlinal axis. A synclinal axis. A valley of elevation. A valley of subsidence. [Illustration: Fig. 54.] [Illustration: Fig. 55.] [Illustration: Fig. 56.] When are strata unconformable? What other disturbances have taken place in the strata? When did these various disturbances take place?