138 RECORD OF SCIENCE FOR 1887 AND 1888. 



and those that arc very diifereutly situated. If the law prove satis- 

 factory in all cases, we shall have a probability of its universality in- 

 creasing Avith the progress of astronomy." But, although this proba- 

 bility may be verj^ great, it can not constitute a i^roof offering the char- 

 acter of experimental certainty which clothes the law of Newton itself 

 in our planetary system. 



A serious difticnlty is encountered in the enormous velocities with 

 which quite a number of stars appear to be moving through space, "run- 

 away" Groombridge — 1830, ji Cassiopea;, y5 Hydri, a Bootis, and others. 

 Some of these velocities are comparable to that of a comet in close prox- 

 imity to the sun, but in most cases there is no visible object near the 

 one in motion to which Ave can ascribe an attractive force, acting accord- 

 ing to the Newtonian law, which would produce the velocity observed, 

 unless we assume enormous masses. 



An interesting article upon this subject is contributed by M. Tisse- 

 rand to the Bulletin Astronomique for January, 1887. 



Milan Double star ohservations. — Professor Schiaparelli has published, 

 in the Milan volume 33, his first series of double star observations made 

 at that observatory with the 8-inch refractor from 1874 to 1885. There 

 are four hundred and sixty-five stars in his list, and in most of them 

 the components are less than 5" apart. In an appendix are given the 

 mean results for a number of the closest pairs as measured with the 

 18 inch refractor. With this instrument he discovered that the princi- 

 pal star off Hydriii is itself a very close double, the magnitudes of the 

 two components being 4 and 5.5, and distance 0".2 or 0".25. The first 

 part of the volume contains a detailed description of the optical per- 

 formance of the 8inch refractor, a discussion of the errors of the mi- 

 crometer and of the accidental errors of observation, and a very full 

 comparison with Dembowski's measures. The differences in the deter- 

 mination of position angle due to the varying inclination of the line 

 joining the two stars to the line of the observer's eyes are also investi- 

 gated, but the reversion prism was not used. Professor Schiaparelli 

 finds that his measures of distance are free from systematic errors, due 

 to personality, but his position angles have a tendency to be small as 

 compared with those of other observers. 



Professor Hough has published a catalogue of two hundred and nine 

 new double stars discovered and measured by himself with the 18}-inch 

 refractor of the Dearborn Observatory. Short lists of new doubles 

 discovered with the McCorinick 2G-inch, and the Lick 3G-inch, have also 

 been published. Burnham's list of his discoveries Avith the 36-incli re- 

 fractor in three months is very interesting, containing as it does ncAV 

 companions to y Cassiopejie, 11 mag., 2".2 distant; and a Tauri, 12 mag., 

 2".3 distant. 



The following table contains the results of recent computations of 

 the orbits of binary stars. The star S Equulei is of especial interest, 

 as the period of eleven and a half years assigned to it is the shortest of 



