Our Astronomical Column.

Abstract

THE CAPE OBSERVATORY.—The second portion of the data upon which the forthcoming Cape Catalogue for 1885 will be founded has recently appeared. The first portion, containing the results of the meridian observations made during the years 1879, 1880, and 1881, was published by Dr. Gill some time ago, and the present volume gives the results from the beginning of 1882 to February 8, 1885, when, the programme for the observation of the fundamental stars of Schönfeld's Durchmusterung—which stars will form the most important part of the Catalogue—having been completed, further work with the transit instrument was suspended. An additional reason for the interruption of the meridian observations lay in the desirability of re-polishing the object-glass, and of replacing the micrometer screws of the circle microscopes, which were of gun-metal, by steel screws. The investigation of the errors of the screws used in the present observations forms the most important portion of the introduction, for the effect of wear upon them has attracted Dr. Gill's special attention, and has already formed the subject of a lengthy paper by him in the Monthly Notices of the R.A.S., vol. xiv. The transit instruments of the Cape and Greenwich Observatories are almost exactly alike in construction; it is therefore interesting to note that there are evident differences in their behaviour; thus the mean horizontal flexure of the Cape instrument, as determined by the collimators, amounts to nearly half a second—0″.462—whilst that of the Greenwich telescope is almost insensible.