SCIENCE.
��FRmAT, MARCH i
��COitMEST AND CRITICISM. A THOROUGH and systematic scrutiny of the heavens Tor stars of Inrge iiarallax, or stars comparalively near our solnr system, bas long been r^aidcd a desideratum in astronomy. The bearings of such researi'li on the laws of distribution of the stars tbroughout tlie uni- verse of space are such that no substantial progress in the discovery of these laws can be made until the parallaxes, or what is the same thing the distances, of a large nnmber of suit- ably chosen stars have become known. The determinalioD of the parallax of a star neces- aitnles the exercise of the utmost skill of the observer, and taxes to no small degree the judgment of the computer in reducing the ob- servations ; and only a few astronomers have been icnourn to undertake the task. The par- allaxes of two or three stars only have been determined by American astronomers, among whom Professor Hall of Washington is fore- most, if not alone. He boa also called atten- tion in the Analyst to the facility with which the work may be conducted by a careful ob- aerver, and bas developed the necessary for- mulas of reduction in such attractive shape that it is rather remarkable that so few of our observatories have engaged in the work. We commend it to good observers looking aliout for the opportunity of employing a mo<lerate
eunental outfit to the best advantage, ien, however, we come to the deter- Uon of parallaxes in bulk, astronomers everywhere seem to have shrunk from the ondertaking, each wailing for another to lead, until Dr. Ball, astronomer royal of Ireland, mode a serious beginning of the task, about eight years ago, at the observatory of Trinity college, Dublin. While others have been con- tent to measure and reduce the parallax of a Ko.m — 1M&.
��single star occasionally. Dr. Ball is encouraged by the contemplation of a working-list of some nine hundred stars, and he has already com- pleted and published his work upon nearly one- half of this number, — an unparalleled labor in this branch of astronomy.
We should mention here, also, the determi- nations of stellar distances made in the south- ern hemisphere by Dr. Gill and Dr. Elkiu, the results of which indicate extraordinary pre- cision of measurement. With renewed enthu- siasm in this research, these astronomers have outlined a plan of operations which contem- plates an extended parallactic survey of the stellar heavens, and which may be expected to be brought to a conclusion in eight or ten years. Dr. Elkin is already engaged in the preliminaries of the work with the fine heli- ometer belonging to the obser\'atory of Yale college ; and Dr. Gill has only lately placed with the Messrs. Rcpsold of Hamburg the contract for a new heliometer of seven inches aperture, — the largest ever constructed. In about two years from the present time he will begin at Capetown his part of the work of carrying out this conjoined programme of par- allax research.
Mant have remarked the gradual assimila- tion of scientific discoveries by the o* n-iAAw. To us the process seems comparable to the percolation practised by the pharmacist. He takes good alcohol, and pours it on the dmg of which he desires to extract the active prin- ciple. The spirit gradually soaks down through the substance, extracting its soluble portions, and issues from the lower end of the percolator, much changed in character. Usually, in the case of the druggist, the result is satisfactory ; but, when scientific facta — the pure alcohol of science — are concerned, the additions received by percolation are almost invariably of such a nature that the percolate is useless. This is
�� �
