Licence: Public Domain Mark
Credit: Physical geography / by Mary Somerville. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![countries liad escaped the wreck of time, and that their inhabitants had dwindled under the change of circumstances. The Mega- therium and Equns curvidens, or extinct horse, had so vast a range in America, tliat Avhile Sir Charles Lyell collected their bones in Georgia in 33° N. latitude, ]Mr. Darwin brought them from the cor- responding latitude in South America. The Equus curvidens difl'ered as much from the living horse as the quagga or the zebra does, and the fossil horse found in Em-ope is also probably a dis- tinct and lost species. A compai'isou of the fossil remains with the living forms has shown the analogy between these beings of the ancient world and those that now people the earth ; and the greatest triumph of the naturalist is the certainty with which he cau decide upon the nature of animals that have been extinct for thousands of years, from a few bones entombed on the earth's surface. Ouvier will ever be celebrated as the founder of this branch of comparative anatomy, which Professor Owen, in our own country, and following in his steps, has so much extended. Among many other important discoveries, he has found, by microscopic observation, that the structm-e of the tissue of Avhich teeth are formed is difterent in dilferent classes of animals, and that the species can in many instances be determined from the fragment of a tooth. A small portion of a bone enabled him to decide on the nature of the extinct race of gigantic bu-ds which formerly inhabited New Zealand, and the subsequent dis- covery of the entire skeleton confirmed the accm-acy of this deter- mination. The greater part of the continents in the N. hemisphere was elevated above the sea during the Tertiary period, and such lauds as already existed acquired additional height; consequently the climate, which had previously been warm and equable, became gradually colder, for an increase of land, which raises the tem- perature between the tropics, has exactly the contrary eflect in higher latitudes. To this cause, and especially to the increase of laud in and near the Arctic circle, may be attributed, perhaps, the greater degree of cold that appears to have prevailed during the latter part of the Pliocene period, when a large extent of the European continent was covered by an ocean full of floating ice, not unlike that seen at this day oft the N.E. coast of During the latter part of the Pliocene period, however, the bed of 1 If a line be drawn from the north-eastern coast of Xorth America within the limit of floating: ice, and if it be continued across tlie southern half of Ireland and England, and prolonged eastward so as to strike against the Ural mountains, it will mark the boundary of the European portion of](https://iiif.wellcomecollection.org/image/b21961086_0048.jp2/full/800%2C/0/default.jpg)
