to deduce completely trustworthy conclusions concerning the climate of a given geological period by an examination of its fossil remains. In Eocene times, or at the beginning of the Tertiary Period, the climate of what is now Western Europe was of a tropical or sub-tropical character, the Eocene beds being found to contain the remains of cowries and volutes, such shells as now inhabit tropical seas, together with the fruits of palms and remains of other tropical plants. And further, it has been shown that in Miocene times, or about the middle of the same epoch, the central parts of Europe were peopled with a luxuriant flora resembling that of the warmer parts of the United States, and that Greenland, now buried for the most part beneath a vast ice-shroud, was warm enough to support a large number of trees, shrubs and other plants that are at present denizens of the temperate regions of the globe. And lastly, from the study of fossils, geologists first learned to comprehend a fact, that is, that the crust of the earth is liable to local elevations and subsidences, which may be regarded as of cardinal importance in all modern geological theories and speculations. Long after the remains of shells and those of other marine animals were first observed in the solid rocks constituting the dry land, and at great elevations above the sea-level, attempts were made to explain this unintelligible phenomenon upon the hypothesis that these remains or fossils were mere _lusus naturæ_, due to some “plastic virtue latent in the earth.” But the common-sense of science soon rejected this idea, and it was universally agreed that these bodies were really the relics of animals that once lived in the sea. When once this was admitted, further steps in the right way of thinking became comparatively easy, and at the present day no geological doctrine stands on a surer foundation than that which teaches that our existing continents and islands, fixed and immovable as they appear, have been repeatedly sunk beneath the ocean and just as repeatedly been lifted above its waters. Not only have fossils an important bearing upon geology and physiography as has been seen, but they have relations, most complicated and weighty in character, with the science of biology, or the study of living beings. No adequate understanding of zoölogy and botany is possible without some acquaintance with the types of plants and animals that have passed away, for there are numerous speculative problems in the domain of vital science, which, if soluble at all, can only hope to find their key in researches carried out on extinct organisms.