4 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



or v v F; from l s OS-7 7 it was again p B. It deserves at- 

 tention. 



In Vol. III. of the Moscow Observations, Professor Bredi- 

 chin has given his observations to determine the parallax of 

 the nebula II iv. 37. The series extended over sixty-five 

 nights, and comprised eight measures of Ac on each, night. 

 The observations are grouped into twelve groups. The par- 

 allax resulting is 0.065" 0.040". This includes the tem- 

 perature correction of the screw. If the mean value of the 

 screw be used without such correction, the parallax results 

 as 0.009"0.041". Thus this nebula appears to be at the 

 same distance as the (single) comparison star. 



Dr. Dreyer has published his supplement to the "General 

 Catalogue of Nebulae and Clusters of Stars"' (Herschel). It 

 contains, first, notes and corrections to the catalogue ; and, 

 second, a continuation of this. The numbering is continued 

 from 5079 (Herschel's highest number) to 6251. Of course 

 this sum includes errors, duplicates, possible comets, etc., and 

 on this account it has been doubted whether the time for the 

 systematic catalogue of Herschel had come in 1864. The 

 immense convenience of it as a printed working-list quite 

 overbears any possible want of logical arrangement ;. and Dr. 

 Dreyer's work is a much-needed supplement, and is edited 

 with great care. 



Dr. Doberek has given in Nature (February 14, 1878) an 

 abstract of D' Arrest's Undersogelse on spectra of nebulous 

 stars, which will be valuable "to English readers, the original 

 paper being almost unknown. About 6000 nebula' were 

 known in 1872; of these 150 have been examined with the 

 spectroscope only one-fortieth part. Of these about three 

 fourths give the continuous spectrum, while only one fourth 

 are true gaseous nebulae. Gaseous nebulae are, with few ex- 

 ceptions, characterized by greenish-blue light, sharply defined 

 circular or elliptic disks, and often have bright condensations 

 within, almost stellar in appearance. A few are, however, 

 large, irregular, and complicated, like nebula Ononis, for ex- 

 ample. The ray-like elongated nebula) are, so far, always 

 characterized by a continuous spectrum. The characteristic 

 lines of a gaseous nebula have the wave-lengths, according 

 to D'Arrest, (A) 5004.0, (B) 4956.6, and (C) 4860.6, with a 

 fourth line occasionally present. From a great number of 



