Page:Popular Science Monthly Volume 4.djvu/263

Rh pellicle, resembling cobweb, which being removed, the cocoon is found to be oval. In color it is grayish, and its tissue differs from that of European cocoons in being wove like a bird's-nest. The caterpillar does not shut itself quite up in the cocoon, but leaves an opening, through which it escapes in the imago-shape.

The Bombyx saturnia works rapidly, completing the cocoon in three weeks; in three weeks more it quits it; and thus the silk-harvest takes up only six or seven weeks. The process of filature, or of unwinding the threads of the cocoon, is very simple, the threads, owing to the peculiar structure of the cocoon, being very readily separated from one another by the action of warm water. The fibre possesses considerable strength. One thread, twelve inches long, will bear a weight of sixty-two grains, and a cord of fifty-four threads a weight of over two pounds. The thread, however, is somewhat coarse, but efforts are being made to get it of greater fineness so as to fit it for weaving into fabrics and spinning into sewing-thread. If this Brazilian fibre passes successfully through its period of trial and experiment, it will give the world a very cheap silk, the cost of production being much less than that of European silk. The cocoon is found in great quantities in the north of Brazil. The caterpillar feeds on the tree, and withstands the inclemency of the weather. The tree is so abundant that whole ship-loads of cocoons might be collected.

The Descent of Man..—M. Gabriel de Mortillet, at the recent meeting of the French Association, after showing that certain flints found in tertiary strata bear evidences of human workmanship, goes on to prove that this tertiary precursor of man was not identical in species with the man of the present period. "If there is one fact well established," says he, "and admitted by all, it is this: that there is a succession of faunæ from one geological period to another. From stratum to stratum the fauna is modified, the animals change, and these modifications, these changes, are all the more marked in proportion as the strata are wider apart. Between two strata in contact there may exist species in common, but strata widely separated from one another have different species, and even different genera, in case they lie very wide apart. These changes occur all the more rapidly in proportion as the animals possess a more complicated organization. Thus the mollusca, having a less complicated organization than the mammals, have sometimes a far more protracted existence as species. Certain shells are found identical in two strata, in which the mammalian faunæ are very widely different. These are not mere hypotheses, but scientific data, based on direct observation of facts.

"Now, since the formation of the calcareous strata of Beauce and of the loam-deposit at Thenay, in which chipped flints are found, the mammalian faunæ was completely renewed at least three times. The differences between the mammals of the Beauce limestone and the mammals of the present period are not only sufficient to characterize distinct species, but have appeared sufficient in the eyes of zoologists to warrant their classification into special genera. The mammals of the level of the Beauce limestone and of the Thenay loam all belong, almost without exception, to extinct genera—genera nearly allied to those at present existing, but yet quite distinct from them. How, then, could man, who has a most complicated organization, alone escape the action of this law? We must therefore conclude that, if, as every thing leads us to presume, the Thenay flints bear the evidences of intentional chipping, they are the work, not of the present human species, but of another species of man, possibly even of a genus the precursor of man, which would serve to fill up one of the gaps in the zoological series."

An Ancient Papyrus.—The King of Saxony has purchased, and placed in the Leipsic Library, an Egyptian papyrus on the preparation of medicines, which was found at Thebes by Dr. Ebers. It is a beautiful yellow papyrus, in a good state of preservation. It consists of 110 columns, and has written on the back a double calendar in eight columns. Each column is eight inches wide, and contains twenty-two lines. The writing is from right to left; it is all in black ink, except the beginnings of chapters,