690 



SCIENCE. 



[N. S. Vol. XVI. No. 409. 



inches aperture and five feet focal length 

 at Greenwich, near the Royal Observatory. 

 Groombridge labored for several years in 

 observing the stars of the northern heavens. 

 After his death in 1832, the reduction of 

 these observations was superintended by 

 Airy and a valuable catalogue of 4243 stars 

 reduced to 1810.0 was formed. Airy pro- 

 nounces the work ' one of the greatest which 

 the long-deferred leisure of a private indi- 

 vidual has ever produced. ' This catalogue 

 is not exclusively circumpolar, as many 

 stars of forty or even fifty degrees of north 

 polar distance are included. The Groom- 

 bridge stars were reobserved by Johnson at 

 the Radcliffe Observatory of Oxford Uni- 

 versity during the years 1840 to 1853 and 

 the results form a part of the Radclifi'e 

 Catalogue of 6,317 stars for 1860.0. More 

 than 85 per cent, of the Groombridge stars 

 were observed at Greenwich during the 

 years 1887 to 1896, and are contained in the 

 second Greenwich 10-year Catalogue for 

 1890.0. 



Another useful piece of amateur work 

 is the Redhill Catalogue of 3,735 circum- 

 polar stars for 1855.0 by R. C. Carrington, 

 an astronomer otherwise well known for his 

 work on the sun. His observatory was situ- 

 ' ated at Redhill in the southern suburbs of 

 London, and his instrument, now at the Rad- 

 cliffe Observatory, Oxford, was a transit 

 circle by Sims of 5 inches aperture and 66 

 inches focal length. Carrington extended 

 the zones of Bessel and Argelander from 

 80° north declination to the pole. It was 

 his intention to observe all stars within this 

 region do\\ai to the tenth magnitude. In 

 the introduction to the catalogue Carring- 

 ton states 'I will establish the rule that of 

 the class of stars included in my plan, none 

 shall be excepted from sufficiently repeated 

 observation,' and this resolution seems to 

 have been faithfully carried out. 



Another work of importance is that of F. 

 M. Schwerd, a professional astronomer of 



Speyer in Rhenish Bavaria, not far from 

 Heidelberg. Schwerd observed, during 

 the years 1826-8, 1,397 stars within fifteen 

 degrees of the pole, with a small but ' vor- 

 treffliche'- meridian circle by Ertel of 1.7 

 inches aperture and 42 inches focal length. 

 The divided circle was 20 inches in diameter 

 and the power of eye-piece used was 126 

 diameters. Schwerd 's observations reduced 

 to 1828.0 were published by Wilhelm 

 Oeltzen, of Vienna, in 1856. 



The observations of circumpolar stars by 

 Lalande at the Paris Observatory have been 

 collected into a catalogue by Fedorenko, of 

 Pulkowa, which, like the catalogue of 

 Groombridge, contains many stars forty 

 degrees or more from the pole. This cata- 

 logue contains 4673 stars for 1790.0. 



A valuable recent work is the catalogue 

 of 123 circumpolar stars for 1893.0 by M. 

 Ditchenko, of Pulkowa. The stars of this 

 catalogue are all within ten degrees of the 

 pole and mostly of the 7.0 magnitude or 

 brighter. The observations were made with 

 the Repsold Meridian Circle of the Pul- 

 kowa Observatory and are differential, be- 

 ing based on the nine fundamental circum- 

 polar stars of the Bet-liner Jahrhuch. The 

 stars have been observed from four to six 

 times each. 



During the past twenty years good differ- 

 ential work on the circumpolar stars has 

 been done in the United States with Rep- 

 sold meridian circles at the Williams Col- 

 lege Observatory, Williamstown, Mass. ; at 

 the Washburn Observatory, Madison, Wis. ; 

 and at the Lick Observatory. A few obser- 

 vations of circumpolar stars on a funda- 

 mental basis have within recent years been 

 made at the Naval Observatory in Washing- 

 ton, but very little really fundamental work 

 on the fixed stars seems to have been done 

 in this country. 



Dr. Auwers, of Berlin, published in 1897 

 (see A. N. Nr. 3440) a list of 21 circum- 

 polar stars, with a request for observations 



