Scientific Serials

Abstract

Journal of the Franklin Institute, November 1871.—The editorial notes in this number are as usual very instructive; amongst them we must notice Young's catalogue of the bright lines observed in the chromosphere of the sun, which have already reached a goodly number. Under Civil and Mechanical Engineering there are several useful and interesting articles, such as “On Woodworking Machinery,” “On the Flow of water in rivers and canals,” &c.—Prof. Cooke contributes the first of a series of papers “on the chemical theory of the Voltaic Battery.” The present communication, however, deals with preliminary matters; it discusses molecules, atoms, and the quantivalence of elements. The paper which follows is “On some improvements in reflecting Telescopes,” by J. A. Hill. The author proposes, in the first instance, to reflect the light from a movable plane mirror placed in the axis of the speculum, which receives the reflected rays; the convergent beam from the speculum passes through an aperture in the centre of the plane mirror, and can be received in a suitable eye-piece; no tubes are used, so that by this method it would be as easy to handle a mirror of 1,000 feet focal length as one of the same size of 50 feet focal length. The observer, too, would remain stationary, and need not be hoisted into mid-air.—Prof. Young continues his Spectroscopic Notes; this month's contribution is “on the construction, arrangement, and best proportion of the instrument, with reference to its efficiency.” Under this head come the best angle and material for the prisms, the means of testing for flatness of surface and homogeneity of substance, and the number and arrangement of the prisms; there are also two other sections, “on dispersive efficiency and on luminous efficiency.” A suggestion of a new form of chemical spectroscope is given, the dispersive part of this consists of two prisms, which are each concave on one side, and are cemented to the convex object-glasses of the collimator and observing telescope. By this it is hoped to save both material and light.