264 THE POPULAR SCIENCE MONTHLY. 



ficient number to establish the orbit. The existence of two inner sat- 

 ellites has since been established, and it is probable that Struve's obser- 

 vations were sometimes on one of them and sometimes on the other. 



The field covered by Struve's subsequent labors is so large and his 

 papers so numerous that it is not easy to give any untechnical account 

 of his works. He has determined the parallax of several stars, made 

 a careful series of observations on the rings of Saturn, made several 

 journeys to observe solar eclipses, and had general charge of the geo- 

 detic operations in the Russian Empire. His greatest recent work 

 has been a continuation of the work of his father on double stars. In 

 1878 the observations of this class, which he had been making for 

 thirty-five years, were all collected and published in the ninth volume 

 of the " Pulkowa Observations." 



In 1862 he succeeded his father as Director of the Pulkowa Observ- 

 atory. Since that time his energies have been as much occupied with 

 the general direction of the establishment as with independent scientific 

 work. His family has been distinguished by the managing capacity 

 and diplomatic skill of its members, some of whom hold high positions 

 in the civil and diplomatic service of the Government. The subject of 

 our sketch is, in this respect, not inferior to his relatives ; and the great 

 efficiency which the observatory has attained under his direction is due 

 as much to his cautious temper, good sense, and judicious management, 

 as to his scientific ability. 



The last enterprise undertaken by Struve is of special interest to us. 

 For many years the great telescope at Pulkowa, and its brother instru- 

 ment at Cambridge, both of fifteen inches aperture, were the largest suc- 

 cessful refractors in the world. With the construction of the eighteen- 

 inch telescope for Chicago in 1862, the introduction of larger instru- 

 ments was inaugurated and continued until the great Washington 

 telescope left that at Pulkowa far behind. This was so far contrary 

 to the ideas of the Pulkowa Observatory that about a year ago the 

 Russian Government authorized Struve to negotiate for the construc- 

 tion of a larger refractor than any yet made. The most difficult and 

 delicate matter was the objective, and, after a visit to the principal 

 European workshops, he determined to come to America for the pur- 

 pose of conferring with Alvan Clark and Sons, and inspecting their 

 chef-d'oeuvre at Washington. On arriving here in August last he spent 

 several weeks in visiting friends and institutions. At the Saratoga 

 meeting of the American Association for the Advancement of Science, 

 he had an opportunity of making the acquaintance of many of our sci- 

 entists. The result of his visit to Cambridge was the completion of a 

 contract with the Clarks for a thirty-inch object-glass, which, it is 

 hoped, may be completed within two years if the glass disks can be 

 procured from the makers of optical glass. The mounting of the tele- 

 scope is to be made by the Repsolds at Hamburg. Having executed 

 his mission, he sailed for his home on September 13, 1879. 



