Page:Popular Science Monthly Volume 29.djvu/292

280 Pennsylvania, from near Doylestown to Maryland, and which, taken together with some parallel dikes of similar nature and composition, northeast of Doylestown, forms a series of nearly continuous dikes some ninety miles in length. In the paper he has published on the subject he shows that, although frequently represented only by a line of loose weathered bowlders, it is practically continuous along a course seventy miles in length. In Bucks County the dike abuts against the south side of a great fault of several thousand feet upthrow, and upward of twenty miles in length, while, at a distance laterally of five miles, another long dike of identical composition and structure abuts against the north side of the fault, and continues thence to the Delaware River. If not the same dike laterally displaced, the two portions clearly belong to the same system, and were produced by a single cause. It is said that this dike was used during the war of the rebellion by the negro slaves as a guide in their flight northward. Several of the stations of the underground railroad are said to have been on or near its line; and the negroes were directed to follow these black rocks across fields and through woods "until they were led into the hospitable regions of Chester and Bucks Counties."

The Magnitude of Dr. Gould's Astronomical Work.—At the complimentary dinner given to Dr. B. A. Gould in Boston, in May, 1885, Professor W. A. Rogers, of Harvard Observatory, made a suggestive comparison of the work which Dr. Gould has done at Cordoba, in the Argentine Republic, with similar work done previous to 1872. There are, he said, in the northern heavens about 4,500 stars visible to the naked eye; while within the same limits there are about 95,000 stars as bright as, or brighter than, the ninth magnitude, which are usually observed in narrow belts or zones, and are referred to as zone-stars. The bright stars are common to nearly all general catalogues, but the positions of the fainter stars depend, for the most part, on two or three separate observations. Dr. Gould has formed two catalogues since 1872—a general catalogue of stars extending to the south pole, containing 34,000 stars, and a catalogue of zone-stars, numbering 73,000. The two catalogues represent about 250,000 separate observations. It is stated in one of the printed volumes that the chronographic register of the transits, the pointing of the telescope for declination, have all been done by Dr. Gould personally. The number of distinct and separate observations involved in this work must certainly exceed a million. The whole number of stars in the two Cordoba catalogues is nearly three times as great as in any single catalogue thus far constructed; and it must be remembered in this connection, that the great catalogues of Lalande, of Bessel, of Argelander, and of Schjellerup, represent the labors of a lifetime. The total number of stars in all catalogues formed previous to 1870 is about 260,000, as against the 105,000 stars in the Cordoba catalogues. Since 1869, a confederation of fourteen observatories, situated in different parts of the world, has been engaged in the accurate determinations of the positions of the 100,000 stars to the ninth magnitude in the northern heavens. Up to 1882, a total of about 346,000 observations had been made. Considerable progress had been made in this work before Dr. Gould left this country for South America. His work, involving two thirds as many observations as all others combined, is completed, and is all in the hands of the printer, while the actual formation of the catalogue to be issued under the direction of the Astronomische Gesellschaft can hardly be said to have been begun.

Japanese Camphor.—Camphor is very largely exported from the Japanese island of Kiu Shiu, where the tree grows abundantly in all situations. Many of the trees reach a great size, some near Nagasaki being said to be ten or twelve feet in diameter, while at other places are trees measuring twenty feet across; after forming a trunk twenty or thirty feet high without limbs, the tree branches out in all directions, forming a well-proportioned and beautiful evergreen mass. The leaf is small, elliptical, slightly serrated, and of a vivid dark green. The berry grows in clusters, and resembles a black currant. The wood is valuable for cabinet-work and for