SCIENCE. 



FRIDAY, MARCH 20, 1885. 



COMMENT AND CRITICISM. 



A thorough and systematic scrutiny of the 

 heavens for stars of large parallax, or stars 

 comparatively near our solar system, has long 

 been regarded a desideratum in astronomy. 

 The bearings of such research on the laws of 

 distribution of the stars throughout the uni- 

 verse of space are such that no substantial 

 progress in the discoveiy of these laws can be 

 made until the parallaxes, or what is the same 

 thing the distances, of a large number of suit- 

 ably chosen stars have become known. The 

 determination of the parallax of a star neces- 

 sitates 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 known 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 has also called atten- 

 tion in the Analyst to the facility with which 

 the work ma} T be conducted by a careful ob- 

 server, and has 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 about 

 for the opportunity of employing a moderate 

 instrumental outfit to the best advantage. 



When, however, we come to the deter- 

 mination of parallaxes in bulk, astronomers 

 everywhere seem to have shrunk from the 

 undertaking, each waiting for another to lead, 

 until Dr. Ball, astronomer ro}'al of Ireland, 

 made 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 



No. 111. — 1885. 



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. Elkin, 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 

 3'ears. Dr. Elkin is already engaged in the 

 preliminaries of the work with the fine heli- 

 ometer belonging to the observatory of Yale 

 college ; and Dr. Gill has only lately placed 

 with the Messrs. Repsold 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. 



Many have remarked the gradual assimila- 

 tion of scientific discoveries by the ol ttoAAoi. 

 To us the process seems comparable to the 

 percolation practised b} T the pharmacist. He 

 takes good alcohol, and pours it on the drug 

 of which he desires to extract the active prin- 

 ciple. The spirit gradually soaks clown 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 facts — 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 



