What peculiarity in reference to fossils will characterize the deep-sea deposits? How is coal shown to be of vegetable origin? Why will the drift wood of the sea accumulate in particular localities, and why will it sink? Why will it become buried beneath earthy matter? How is it known that wood thus buried will, at length, become lignite? How is lignite converted into mineral coal? What is the proof of it? Have beds of coal been formed at other periods, besides the carboniferous? Is it probable that coal-beds are now forming? How did the flora of the carboniferous period differ from the existing flora? [Illustration: Fig. 76.] Are the alternations of the earthy and coal strata satisfactorily explained? In what portions of the geological series are the deposits of salt found? Where is saline matter principally stored? Explain the conjectural formation of salt in the Mediterranean Sea. What form do rocks take when deposited from a chemical solution? How is sand or gravel solidified by the infiltration of mineral waters? What is the effect of drying upon the solidification of rocks? What is the effect of pressure? What of heat? SECTION V. What is a glacier? What is the extent of the glaciers of the Alps? What change does the mass of snow in the higher valleys of the glacier mountains undergo? What is the source of supply to the glacier? What is the cause of the motion of the glacier? What is the usual annual motion? Why will the glacier melt but little at its under side? Where will the waste at the surface just equal the addition? What circumstances vary the position of the terminus of the glacier? [Illustration: Fig. 77.] What, besides snow and ice, enters into the composition of a glacier? How are these materials supplied? How is a lateral moraine formed? What effect has the motion of the glacier on the rocky surface over which it passes? What is the material by which this effect is produced? How is the terminal moraine produced? How may the moraines on the Jura Mountains be explained? How has it been proposed to explain the striated surfaces of rocks found in the north of Europe and America? What is the objection to this extension of the glacier theory? How does the ice accumulate along the coast in high latitudes to form icebergs? Why does it ultimately separate from the shore? How does it become freighted with earthy matter? In what direction do the icebergs float, and why? What are the dimensions of an iceberg, estimated from the part that is visible? [Illustration: Fig. 78.] Where does the mass of ice increase, and where diminish? What will be the effect of its melting? How is it supposed that icebergs may have striated the rocky surface? What is probably the condition of the bed of the seas over which icebergs now float? Has the north of Europe and America been so depressed, during a period comparatively recent, as to admit of this explanation of the drift phenomena? SECTION VI.