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THE POPULAR SCIENCE MONTHLY. 



emplified in a cast-iron mold divided cen- 

 trally 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 to- 

 gether. The combination has been pro- 

 duced 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 pur- 

 poses, need to be backed by a tougher ma- 

 terial competent to resist strains and great 

 vibration. 



Hedgehogs and their History. — Profess- 

 or Grant Allen, writing in an English paper 

 of the structure and habits of the hedge- 

 hog, observes that the curious spines the 

 animal wears on his back are a feature very 

 apt to recur among animals of diflferent 

 classes the world over, which are much ex- 

 posed to carnivorous enemies. The porcu- 

 pine, a rodent in no way related to the 

 hedgehog, and the Australian echidna, al- 

 lied 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, be- 

 cause only those which happened to be so 

 protected have managed to escape the per- 

 sistent attention of a million generations of 

 vermin-eating carnivores. Hence they are 

 apt to be either prickly, as in these in- 

 stances, or else protected by a regular cov- 

 ering of bone-like hardness, as in the ar- 

 madillo, the poyou, the pangolin, and the 

 scaly ant-eaters. The spines of the hedge- 

 hog 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 sin- 

 gle blow. They are the result of slow and 

 constant modification in a long line of an- 

 cestors, and not a few intermediate forms 

 arc still in existence to show us, either di- 



rectly 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 an- 

 other animal of the same island still more 

 closely approaches the hedgehog in the 

 greater spininess of its body and in the pos- 

 session of the power of rolling itself up. 

 " Finally, we get in Europe and Asia sev- 

 eral kinds of genuine, fully developed hedge- 

 hogs, 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." 



Scienee In Brazil. — M. de Quatrefages 

 recently improved the occasion of presenting 

 to the French Academy of Sciences a num- 

 ber of documents from the Brazilian muse- 

 um 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 govern- 

 ment, 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 pur- 

 poses of public instruction. The first four 

 volumes of the archives of the- National Mu- 

 seum are mai'ked by many valuable essays, 

 among which were spoken of, as particularly 

 deserving attention, the studies of Dr. Pizzar- 

 ro on a curious batrachian, and of M. Fred- 

 erick 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 num- 

 ber of tribes from the extreme northwestern 

 part of the continent to Brazil, of boring the 



