Page:Popular Science Monthly Volume 19.djvu/815

Rh by Mr. Tebbutt, of New South Wales, Australia, on May 22d. During the interval between these two dates it had moved northward through an arc of more than 60°, which rapid motion accounts for its sudden apparition in our northern sky.

The relative situation of the orbits of the comet and the earth will be best understood by the perspective view of a model of the two orbits constructed to scale (Fig, 2). This model was executed, from elements computed by Messrs. Chandler and Wendell, of Harvard College Observatory, by Ensign S. J. Brown, U.S.N., who kindly placed it at the service of the writer.

In this cut, the horizontal plane represents the position of the earth's orbit, and the plane cutting this at a large angle represents the plane of the comet's orbit. The comet moved from below, which is the southern side, up through the plane of the earth's orbit to the northern side. The dates indicate the positions of the earth and comet at different times in their respective orbits. It passed its perihelion point just before passing through the plane of the earth's orbit.

The orbit of the comet is inclined to the plane of the earth's orbit at an angle of 63°. Its perihelion distance is 0·77 of the earth's distance from the sun. It arrived at its perihelion June 16th, and was nearest the earth June 19th, when its distance from the earth was 0·28 of the earth's distance from the sun.

The nucleus attained fully the brightness of a first-magnitude star, and the length of the tail was variously estimated at from 20° to 30°. This comet is still faintly visible to the naked eye (August 22d).

At first it was suspected that this comet was identical with that of 1807, but later investigation disproved this supposition.



HE great body of the theoretical and practical knowledge which has been accumulated by the labors of some eighty generations, since the dawn of scientific thought in Europe, has no collective English name to which an objection may not be raised; and I use the term "medicine" as that which is least likely to be misunderstood; though, as every one knows, the name is commonly applied, in a narrower sense, to one of the chief divisions of the totality of medical science.