[10] Nature Reader, No. 2, Lesson 33. [11] Nature Reader, No. 2, Lesson 12. [12] See Lesson XVI., p. 119. LESSON IV. THE REIGN OF THE PINES AND THE REPTILES. “A monster then, a dream, A discord. Dragons of the prime, That tear each other in their slime, Were mellow music, matched with him.”-- --TENNYSON, _In Memoriam_. [Illustration: GNOMES IN A CAVE AT WORK.] We have now reached the middle period of the earth-building story. We have thus far seen how from a great globe of burning gas, our earth shrank, cooled, hardened, became wrapped in waters, uplifted continents and islands, and through successive periods became filled with plants and animals of sea and land. The period at which we have now arrived was the age of wonderful monsters, of pines, and of palms. For the first time also the earth was splendid with flowers. The seas grew constantly cooler, and the earth crust as constantly thickened. As the seas cooled less vapor rose into the air, the atmosphere cleared, and a bright sunshine poured over the continents. The continents of this middle period of world-building were some of them larger than now. Probably North America stretched over much nearer to Europe; England was not an island, but was joined to the mainland of Europe, and extended far south and west in what is now the sea. The mountains were very high, so high that it has been supposed that they had snow-covered tops, and glaciers formed in their gorges, and icebergs, breaking from the glaciers, sailed off to distant seas. At this time the earth was green with ferns and grasses and dark with forests. Among the most noble of the trees were the cycads. They were partly like pines, and partly like palms. Beside the cycads grew great pines, and probably pines were the distinguishing trees of this cycle. The vegetation was more like the present vegetation of the tropics than like that of northern climates, because the earth was warmer then than now. In our last lesson we spoke of the red sandstone as a very rapid deposit of sand by water. When the deposit is slow, the red color is washed out of the sand by the action of air and water. This red of the red sandstone is due to iron-rust, which stains the sand as it does iron or steel. When the deposit of these stained sands is rapid, in thick beds, the color does not have time to bleach out. There are two vast layers of this red sandstone, the old and the new. The new is largely present in the beds of the middle period of world-building, and sometimes gives the first age its name--the age of the New Red Sandstone. The northern shore of Scotland is banded by the old red sandstone, as if held in a sandstone frame.