442 SCIENTIFIC RECORD FOR 1885. 



Young {Obsermtory, viii: 173, May, 1885): "On the whole, I find also 

 true what Mr, Clark told me would be the case on first mounting our 

 23-inch instrument, that I can almost ahrays see with the 23inch everything 

 I can see with the 9^-inch, under the same atmospheric conditions, and see 

 it better; — if the seeing is bad, only a little better, — if good, immensely 

 better. The only exceptions are in the case of objects which require a 

 very low power, lower than any that can be obtained with the eye-i>ieces 

 of the large telescope." 



The great Pulkoica refractor. — "M. Struve was chiefly occupied during 

 the year with work incidental to tlie installation of the great 30-incli 

 refractor. It was anticipated that by September, 1884, things would 

 be in such a state that it would be possible to begin to observe with 

 this gigantic instrument; but, owing to various delays, chiefly connected 

 with the construction of the dome, it was not until the end of Septem- 

 ber that the Eepsolds could be invited to come to Pulkowa to superin- 

 tend the work of erecting the telescope; this was accomplished very 

 successfully by them in about three weeks. And M. Struve expresses 

 himself as greatly pleased with the ease with which the telescope can 

 he set, with the equality of the illumination on all its parts from a sin- 

 gle lamp, with the accuracy with which the driving-clock performs, and 

 with the facilities for altering the telescope into a powerful spectroscope; 

 so that this great instrument may be regarded as the successful out- 

 come of the highest skill of modern art in this department. Further 

 work on the dome was interrupted by the approach of winter. - - • 

 At present the dome is moved by hand ; it is hoped, howev^er, that this 

 may eventually be done by electricity, and that a motive power will 

 thus be obtained sufficient to overcome the hindrances to the rotation 

 of the dome arising "from snow and frost. From investigations made 

 by H. Struve it appears that the position of the polar axis is correct to 

 a fraction of a minute, that the change in focal length of the instrument 

 during the winter is but trifling, and that, notwithstanding the great 

 weight of the object-glass and of the eye-end, the flexure of the tele- 

 scope is so small as to be practically insensible. M. Struve proposes to 

 use the great refractor for observing such double-stars as. are beyond 

 the reach of the 15-inch equatorial, and to undertake observations of 

 certain interesting nebulae, as well as spectroscopic researches on stars 

 in cases where the great optical power of the instrument will make the 

 observations of special value." {Observatory.) 



" Science " (vi : 306) publishes a letter from Dr. Otto Struve to Alvan 

 Clark & Sons, from which we make the following extract : "I am asked 

 by the Government to inform you that, in acknowledgment of the ex- 

 cellent performances of the great object-glass furnished for Pulkowa 

 by your firm, His Majesty the Emperor has been graciously pleased to 

 confer upon you the golden honorary medal of the empire. The value 

 of this gift is enhanced by the circumstance that this medal is given 



