Page:Popular Science Monthly Volume 24.djvu/636

618 Birds, then, may be roughly described as reptiles with feathers. Professor Huxley was the first to see the real closeness of the connection between the two groups, and to unite them under a common name as Sauropsida. Strictly speaking, the only constant difference between them, the only one distinctive character of birds as a class, is the possession of feathers; and, if, like uncompromising Karl Vogt, we insist upon calling archæopteryx a reptile, because of its anatomical peculiarities, even this solitary distinction must vanish utterly, leaving us no point of difference at all between the two classes. It must be remembered, of course, that all the other characters which we always have in our mind as part of the abstract idea of a bird are either not constant or not peculiar to birds alone. For instance, we usually think of a bird as a flying animal; but then, on the one hand, many birds, such as the ostriches, kiwis, penguins, and dodos, do not or did not fly at all; and, on the other hand, many other creatures, such as the bats, flying-squirrels, flying-lemurs, pterodactyls, dragon-lizards, and butterflies, do or did once fly just as much as the birds. So with their other peculiarities: their habit of laying eggs descends to them from fish and reptiles; their nest-building propensities, which are wanting in some birds, are found in the Australian water-mole, in field-mice, and even in stickleback; and their horny bill, which is almost confined to them, nevertheless occurs again in the ornithorhynchus and in many turtles. In short, every other apparently distinctive point about birds except the possession of feathers either breaks down on examination or else descends to them directly from early unbird-like ancestors. And the first feathered creature of which we know anything, archæopteryx, was at least as much of a reptile as of a bird.—Longman's Magazine.



HE Mexican Republic extends from the fifteenth to the thirtieth degree of north latitude, and embraces an area of about 750,000 square miles. It is traversed by the continuation of the Cordillera of South America, here called the Sierra Madre, which trends north-westerly from the Isthmus of Tehuantepec, and varies in height from a moderate elevation in the southern States of Chiapas and Oaxaca to a mean height in the nineteenth degree of latitude of 9,000 feet, with the peaks of Orizaba and Popocatepetl—"the culminating point of North America"—rising to the elevations of 17,200 and 17,720 feet respectively. On the parallel of 21°, the Cordillera becomes very wide and divides itself into three ranges: one running eastwardly to Saltillo 