132 RECORD OF SCIENCE FOR 1887 AND 1888. 



double mirror at the objective : auy cLauge in the distance between the 

 two stars can then be measured vdth extreme nicety. It should perhaps 

 be mentioned that Houzeau churned to have suggested this principle in 

 1871. 



Diurnal nutation. — M. J>[iesten, in applying Folie's formulfefor diurnal 

 nutation to the Greenwich observations of ;/ Draconis, has found a posi- 

 tive parallax where Main and Downing obtained a negative value, and a 

 constant of aberration more closely agreeing with that generally adopted. 

 Introducing similar corrections in Hall's discussion of the prime verti- 

 cal observations of a Lyr;e has, however, had no appreciable effect. 



STAR- CATALOGUES AND CHARTS. 



Paris Catalogue. — The first two volumes of the great work undertaken 

 by Jjeverrier a third of a ce%tury ago, the re observation of the stars of 

 Lalande's catalogue, have recently been published. The first volume is 

 the first installment of the catalogue proper, viz, stars from 0'' to C' of 

 right ascension, observed during the years 1837 to 1881; the second 

 voUmie gives the separate observation^ Each series when complete 

 will extend to four volumes. The observations were made with the five 

 meridian instruments of the Paris Observatory, and include some 20,000 

 or 30,000 observations made between 1837 and 1854; they have there- 

 fore been divided into three periods, 1837-'53, 1854-'G7, and 1868-'8l, 

 and severally' reduced to the mean epochs 1815, 18C0, or 3875. Obser- 

 vations subsequent to 1881, about one-fourth of the entire number, will be 

 published separately. The present section of the catalogue contains 

 7,215 stars, and represents about 80,000 observations in both elements. 

 It gives for each of the three periods the number of observations, the 

 mean date, the right ascension and north polar distance reduced to the 

 mean epoch, and a comparison with Lalande. The precessions for 1875 

 are also added. The introduction, by M. Gaillot, who has superin- 

 tended the reduction, contains a discussion of the probable errors of the 

 observations, and is followed by a comparison of the present catalogue 

 with Auwers' Bradley, and an important investigation by M. Bcssert 

 of the proper motions of a large number of stars, followed by a table of 

 errors in Lalamle's catalogue which the present and other catalogues 

 have brought to light. 



Cincinnati Zone Catalogue. — Professor Porter has published the re- 

 sults of observations made with a 3-inch transit instrument, at the Cin- 

 cinnati Observatory, upon 4,050 stars between the declinations — 18° 50' 

 and — 22° 20', during the years 1885 to 1887. The faintest stars were of 

 about 8.5 magnitude, and nearly all the stars were observed three times. 

 The observations were made in zones, the telescope being clamped. 

 Tlie transits which were recorded l\v the chronograph were generally 

 taken over five wires, and two bisections were made in declination when- 

 ever time allowed. The probable errors of a single observation are 

 rt 0M23 and ± l.''Sl. An ajtpendix gives tin' [)roper motion of sev- 

 enty-five stars deduced from a comparison with other catalogues. 



