Observations of the apparent distances and positions of 380 double and triple stars, made in the years 1821, 1822, and 1823, and compared with those of other astronomers; together with an account of such changes as appear to have taken place in them since their first discovery. Also a description of a five-feet equatorial Instrument employed in the observations
The frequent and exact determination of the apparent distances and positions of such double stars, as are sufficiently close to be easily measured with micrometers and high magnifying powers, was suggested by Sir William Herschel, more than forty years ago, as an enquiry likely to lead to interesting results, and which has, in fact, in his hands, led to the creation of a new department of physical astronomy, and to the discovery of a class of phaenomena in the sidereal heavens referable to the agency of attractive forces, and analogous to those produced by gravity within the limits of our own system. The immediate object with which the enquiry was commenced, the determination of the existence and amount of annual parallax, was soon lost sight of in the more extensive views of the construction of the universe which unfolded themselves as it advanced, and has not since been resumed; though, from the extreme precision of which it will appear in the course of this paper such measurements are susceptible, owing to the refinements of modern instrumentmaking (a precision not to be looked for in any other class of celestial observations ) and the progress we may yet hope for from farther improvements in this respect, there is every reason to suppose it still the most eligible mode of setting at rest that great question, and to believe that no distant period must put us in possession of something decisive from this quarter, as to the existence or non-existence of an appreciable amount of that element.