INDUSTRIAL PROGRESS DURING THE YEAR 1875. xxxi 



which he calls a scintillometer. He finds that those stars 

 which scintillate or twinkle least are those whose spectra 

 show numerous well-pronounced lines, sometimes united in 

 zones. 



Messrs. Smythe and Duncan have shown that the star 

 known as B.A.C. 793 has an unusual large proper motion, 

 and that it is important to continue observations thereon. 



Especial activity has been manifested in the computation 

 of the orbits of double stars, for which work a great mass of 

 accurate observations has now accumulated, through the la- 

 bors especially of the Struves, Herschel, Dawes, Dembowski, 

 South, and Secchi, not to mention a host of others w r ho have 

 contributed to a less decree. Of those whose orbits have 

 been investigated during the past year, we note that of TO 

 Ophiuehi, as computed by Flammarion ; Zeta Aquarii and 

 Gamma Leonis, as computed by Doberck, of Markree. 



Mr. Alvan Clark calls attention to the rapid angular motion 

 of Ma Herculis. 



An investigation of the movements of the double star 42 

 Comce Berenices has been made by Otto Struve, and his assist- 

 ant Dobiago. They conclude that the most probable period 

 of revolution of the two stars is twenty-five and seven-tenths 

 years ; but the plane of the orbit of these stars passes so di- 

 rectly through the solar system that the elliptic orbit it- 

 self appears as a straight line. The computations of Struve 

 have therefore been based entirely upon the observed angu- 

 lar distances of the two stars. In the course of this investi- 

 gation, Struve takes occasion to state that, in observing very 

 close double stars which appear sometimes as an oblong sin- 

 gle star, the centering of the object-glasses of the telescope is 

 an important consideration, as a very small error would lead 

 to a considerable error in the estimated position-angles of the 

 two stars. 



Another double star whose orbit has been investigated is 

 Eta Coronce, concerning which Mr. Wilson states that recent 

 observations show a systematic divergence from the orbit 

 published in 1856 by Winnecke. The hypothesis that best 

 suits all known observations is that at each successive revo- 

 lution of the stars there exists some shortening of the period. 



One of the most extensive works undertaken by Sir John 

 Herschel was the compilation of a catalogue of all known 



