Page:Popular Science Monthly Volume 24.djvu/442

428 in a cast-iron mold divided centrally by a thin sheet of iron, on one side of which sheet fluid iron is poured, and on the other side fluid steel. The dividing plate should be thick enough to prevent the glowing masses on either side from burning through it, and yet so thin that those masses and it shall become thoroughly welded together. The combination has been produced in five shapes: steel by the side of iron; steel between two layers of iron; iron between two layers of steel; a core of steel with the surrounding shell of iron; and a core of iron with the surrounding shell of steel. This steel-iron may be used for a great variety of purposes in which the hard qualities of steel, enabling it to resist wear and tear, or adapting it to cutting purposes, need to be backed by a tougher material competent to resist strains and great vibration.

Hedgehogs and their History.—Professor Grant Allen, writing in an English paper of the structure and habits of the hedgehog, observes that the curious spines the animal wears on his back are a feature very apt to recur among animals of different classes the world over, which are much exposed to carnivorous enemies. The porcupine, a rodent in no way related to the hedgehog, and the Australian echidna, allied to the ornithorhynchus, have precisely similar spines. "The fact is, almost all surviving members of very low and early groups are extremely likely to have such peculiar spiny or armor-plated bodies, because only those which happened to be so protected have managed to escape the persistent attention of a million generations of vermin-eating carnivores. Hence they are apt to be either prickly, as in these instances, or else protected by a regular covering of bone-like hardness, as in the armadillo, the poyou, the pangolin, and the scaly ant-eaters. The spines of the hedgehog are in reality very hard, bristly hairs, specially developed for purposes of defense. Of course, however, he did not get these most effective chevaux-de-frise all at a single blow. They are the result of slow and constant modification in a long line of ancestors, and not a few intermediate forms are still in existence to show us, either directly or by analogy, the fashion in which the defensive prickles were originally evolved. The bulau, of Sumatra, has a few stout bristly hairs scattered among the fur of its back, and gives the first indication of a tendency toward the production of spines. It can not, however, roll itself up into a ball, like the hedgehog. The tanrec, of Madagascar, is covered with a mixture of hairs, bristles, and true spines; while another animal of the same island still more closely approaches the hedgehog in the greater spininess of its body and in the possession of the power of rolling itself up. "Finally, we get in Europe and Asia several kinds of genuine, fully developed hedgehogs, of which our own English specimen here in the ditch is a typical example. It is not often that all the intermediate stages between two distinct animal types have been so well preserved for us by nature as in this interesting instance."

Science in Brazil.—M. de Quatrefages recently improved the occasion of presenting to the French Academy of Sciences a number of documents from the Brazilian museum at Rio Janeiro, to speak in praise of the scientific progress that has been made in that country under the wise encouragement of the Emperor Dom Pedro II. The government, societies, municipalities, and a host of individuals, are rivaling one another in their zeal for the multiplication of educational establishments and for endowing them as richly as possible. Nearly one sixth of the revenue of the country is applied to purposes of public instruction. The first four volumes of the archives of the National Museum are marked by many valuable essays, among which were spoken of, as particularly deserving attention, the studies of Dr. Pizzarro on a curious batrachian, and of M. Frederick Muller on insects; of M. Lacerda on the poison of different snakes and of a toad; the anthropological labors of MM. Lacerta and Peixoto on the tribe of the Botocudos, and on some skulls found in ancient funeral urns; and a memoir by M. Ladislau Netto regarding American origins and migrations. The last study is based upon the strange custom, which is observed in a large number of tribes from the extreme northwestern part of the continent to Brazil, of boring the