Page:Popular Science Monthly Volume 44.djvu/636

620 gained the heat of the Gulf Stream; thus for the eastern part we have cold accounted for and for the western part heat—but the glacial condition extended the whole length; therefore, while it seems possible that glaciers might form on the western part by reason of the snowfall being great, the case is different for the eastern part, which seems to have been entirely deprived of its vapor-making element, heat, for even under existing conditions the mean temperature of Greenland and Labrador is low and the snowfall light as compared with Alaska. The answer is made to this that western winds carried the moisture-laden atmosphere from the west coast to the east, but these winds would have to cross the Sierra Nevada and Rocky Mountains, forcing them to higher altitudes, resulting in the condensation and precipitation of their vapor upon the mountains. This difficulty is overcome by having recourse to the immense lava outflows, covering thousands of square miles west of the Rocky Mountains, which are supposed to have taken place about the Glacial period; this molten mass is supposed to have generated so much heat as to modify the customary effect of mountain ranges and get the vapor-laden atmosphere to the needed point and thus satisfy the hypothesis, but it offers no explanation of the Glacial period in Europe.

Many leading geologists favor this view, while others think the truth will be found in a combination of the last two hypotheses, both being in some measure contributory to the result.

Fossil man has been found in certain countries associated with the remains of certain animals, among which are the mammoth, woolly rhinoceros, cave bear, fossil horse, Irish elk, cave hyena, cave tiger, reindeer, elk, musk ox, aurochs, hippopotamus, lion, and others. These animals are either now extinct or are, for