6i8 THE POPULAR SCIENCE MONTHLY. 



Birds, then, may be roughly described as reptiles with feathers. 

 Professor Huxley was the first to see the real closeness of the connec- 

 tion 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 archeeopteryx 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 want- 

 ing 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 any- 

 thing, archseopteryx, was at least as much of a reptile as of a bird. — 

 Longman^s Magazine. 



MEXICO AND ITS ANTIQUITIES.* 



THE 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 



* Appletons' Guide to Mexico. By Alfred R. Conkling, LL. B., Ph. B. With Rail- 

 way Map and Illustrations. New York : D. Appleton & Co. Pp. 378. 



