member, account for the inequalities in the moon's motion, but it rested on no independent basis. Since that time, Prof. Newcomb has devised a method of testing this question by totally different means, viz., by an examination of the eclipses of Jupiter's first satellite; and this test has been applied by Mr. Glasenapp, an astronomer of Pulkova. Mr. Glasenapp's researches indicate with great certainty that the earth's rotation is not strictly uniform, and that Prof. Newcomb's hypothesis is sustained. The accurate determination of the amount by which the earth is fast or slow is yet to be reached, but we must accept two important facts as probable: 1. That the earth's rotation time is not strictly constant. 2. That the inequalities in the moon's motion are largely, if not wholly, due to this.
Growth and Reproduction of the Antlers of the Deer.—John Dean Caton, whose observations on the natural history of the American Cervidæ are familiar to the readers of Mr. Darwin's writings, contributes to the American Naturalist for June an important paper on the "Structure and Casting of the Antlers of Deer." He shows, in the first place, the substantial identity of structure between the antlers and the ordinary bones; in fact, the antlers are external bones, of very rapid growth, which mature speedily, die, and are soon thrown off; while all other bones are very slow of growth, and persist through life.
The process of growth is as follows: The old antler having fallen off, the blood-vessels of the periosteum at its butt are ruptured, producing a copious flow of blood. Next, the periosteum grows over the cavity in the top of the pedicel, or process of the skull on which the antler stood. On the approach of spring, this covering becomes inflamed, resembling a blood-blister. It rises up rapidly, new systems of blood-vessels forming in it, till its height is twice its diameter; then an osseous deposit is commenced at the circumference of the top of the pedicel. As this deposit rises it thickens very slowly, the upper extremity presenting a thin, serrated edge. Blood-vessels from the periosteum traverse this tissue, supplying it with nourishment. This is the source of supply from without; but there are internal sources also, viz., arteries passing up through the pedicel, and answering to the medullary arteries of long bones.
At the extremities, first, the deposit of earthy salts goes on till this fills up the canals leading from the periosteum into the bony mass, so that the circulation through them is obstructed; and this process goes on till all communication between the internal and the external blood-vessels is severed. The animal is now prompted, by some natural impulse, to rub off this outer covering, while it is gorged with blood. The cavities in the branches and the upper portion of the beam soon become hardened throughout, and the solid wall in the lower part much thickened. Before the central section has become solid, the nutrient vessels are obstructed below, and the deposit of bony particles arrested, while yet the larger portions of the antler are more or less porous. This makes the antler lighter, without seriously diminishing its strength, for its walls are braced within, in every imaginable direction, by thin plates of bone.
In the mean time, the lower extremity, too, becomes more and more compact, and the pedicel, which, during the active growth of the antler, was open and porous, commences a new deposit of laminæ in its cavities. But now, all sources of nutriment having been cut off, the antler dies, and is removed by a singular process. One of the systems of blood-vessels which supply nutriment to the growing antler commences active operations to undermine it. The absorbents of these blood-vessels attack the point of junction between the antler and the pedicel. They do not carry away the surface of the bone evenly, so as to make it smooth, but, as it were, they remove alternate particles, till the union, which before was so firm that no force could break it at the point of juncture, has become so weakened that the antler is detached by some slight violence.
A Remarkable South American Valley.—According to Iron, the upper valley of the Bio Madeira, one of the chief tributaries of the Amazons, rivals California and Australia in mineral wealth. This valley, which contains about 400,000 square miles, is mar-
