58 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



telescope rests at one end of a horizontal axis, whose opposite 

 end bears a counterpoise of the same weight. The iron pier, 

 with the telescope, admits of being raised a small fraction of 

 an inch, reversed in its position, and set down again, the 

 w^hole operation employing less than one minute, although 

 the weight to be moved amounts to about 2500 pounds. 

 The length of the telescope is seven and a half feet, and the 

 aperture of the object-glass about seven inches. Jovnal da 

 Academia, Lisbon. 



STELLAR PHOTOMETRY. 



The invention by Dr.Zollner,in 1862, of his elegant photom- 

 eter, which is specially designed for the study of the relative 

 brightness of the stars, seems to have given a great impetus 

 to this branch of astronomy. By Zollner's instrument, the 

 determination of the brightness of a star is made a matter of 

 exact measurement, and leads to more correct results than 

 any other method that has as yet been proposed. With the 

 results attained by himself and his colleague, Engelmann, of 

 Leipsic, our readers are already acquainted. The most recent 

 publication in this field of observation is by Lindemann, who 

 has, by using the instrument that belongs to the Imperial 

 Observatory at Poulkova, sought to determine, in a general 

 way, the relation between the intrinsic brightness of the 

 classes of stars that are usually designated as of the third, 

 fourth, and fifth magnitudes, etc. He has extended his la- 

 bors even to the faint stars of the ninth magnitude, and has 

 chosen especially such portions of the heavens for the study 

 as afibrd him groups of stars of the greatest possible variety 

 of magnitudes. Lindemann finds that the comparison of his 

 own work with that of his predecessor in this field. Dr. Rosen, 

 shows such a uniformity in their results as to give great 

 weight to their importance. From 1 75 observations of bright 

 and faint stars, Lindemann deduces as the most probable value 

 of the coeflicient of brightness in passing from one order of 

 magnitudes to the next inferior, the decimal fraction 0.0394. 

 This, therefore, in connection with the results of Rosen, seems 

 to him to justify us in the belief that the mean ratio of the 

 brightness of successive stellar magnitudes, for the stars of 

 Argelander's Durchmusterimg^ can now be considered as 

 quite accurately determined. But, as to the question of the 



