ASTRONOMICAL PHENOMENA AND PROGRESS. 



47 



when all is ready, the whole establishment is 

 to be turned over to the Board of Regents of 

 the University of California, who are to appoint 

 a professor. The institution is to be thereafter 

 the astronomical department of the university. 

 Unless some arrangement can be made for 

 evading the legal difficulty thus arising, the 

 instruments must stand idle for several years 

 to come. 



Two important additions have been made 

 to the great telescopes of the world. The 

 companion of the great Washington telescope, 

 which was nearly finished ten years ago, has 

 since been lying idle in the workshop of the 

 Messrs. Clark, awaiting the completion of the 

 McCormick Observatory of the University of 

 Virginia, for which it was designed. This 

 observatory is now so far completed that the 

 telescope was mounted in the autumn of 1884. 

 The other addition has been the Russian tele- 

 scope of thirty inches aperture, which ranks as 

 the largest refractor yet made. The glass was 

 completed by the Messrs. Clark about the be- 

 ginning of 1883. In the spring following Di- 

 rector Struve visited the United States for the 

 purpose of testing the glass and accepting it if 

 found satisfactory. Having found the result to 

 more than fulfill his best expectations, the 

 glass was shipped to Pulkowa, where it has 

 since laid, awaiting the completion of the 

 mounting, and of the dome which is to contain 

 it. The mechanical difficulties of getting a 

 dome more than sixty feet in diameter into 

 working operation were su^h that the tele- 

 scope could not be mounted until the autumn of 

 1884. The mechanical work of the mounting 

 is, in the number and ingenuity of its devices 

 for convenient use, far ahead of any similar 

 work heretofore devised, and reflects additional 

 credit on the Repsolds, of Hamburg, the re- 

 nowned firm to whom the work is due. The 

 eye-piece alone is a piece of mechanism which 

 in the variety and number of its parts seems 

 to equal the whole outfit of an ordinary ob- 

 servatory. The rigor of the Russian winter is 

 unfavorable to astronomical observations, but 

 it is expected that active work with the new 

 instrument will be commenced early in the 

 spring. 



New Method of mounting Reflectors. The Messrs. 

 Henry, at Paris, have devised a method of 

 mounting the mirrors of great reflecting tele- 

 scopes which, if entirely successful, may result 

 in greatly increasing the limits of size of these 

 instruments. Theoretically, a reflecting tele- 

 scope can be constructed of far greater power 

 than the largest possible refractor, because there 

 is no limit to its size. But in practice it is 

 found that reflectors of more than two or three 

 feet in diameter so change their form by the 

 pressure of their own weight that they can not 

 form good images of a celestial object. The 

 very simple but ingenious device of M. Henry 

 consists in grinding the back of the reflector 

 so that it shall accurately fit upon a stiff disk 

 of the same size and form as the reflector it- 



self. A sheet of fine flannel is then inter- 

 posed between the two, and the reflector is 

 supported upon the flannel. The result of the 

 elasticity of the flannel is that the reflector is 

 sustained with greater uniformity than by any 

 other system. This method is founded on the 

 same general idea as that of the late Dr. Henry 

 Draper, who mounted his reflector with great 

 success upon an air-cushion of rubber. 



Equatorial Conde. This term has been applied 

 to an instrument of new construction recently 

 mounted at the Paris Observatory. The main 

 tube of the telescope is directed toward the 

 south pole, and therefore in the latitude of 

 Paris looks downward at an angle of 48 with 

 the horizon. It is so mounted as to turn round 

 on its own axis, but is otherwise immovable. 

 From its lower end a second tube projects at 

 right angles, so that when the first tube is 

 turned round, this second one sweeps along the 

 plane of the equator. In the elbow at the 

 junction point, a reflector is placed at an an- 

 gle of 45 with each tube. At the end of the 

 second tube is placed a second reflector, 

 mounted upon an axis concentric with the 

 tube, with which it also makes an angle of 45. 

 By turning this second reflector the line of 

 sight is made to sweep along the meridian from 

 one pole to the other. By turning the tele- 

 scope upon its axis it sweeps in right ascension, 

 and thus by combining the two motions the 

 line of sight can be directed to any point in 

 the heavens. The eye-piece being fixed, the 

 observer sits in a comfortable room looking 

 down into the telescope, which he directs from 

 point to point by simply turning one of two 

 handles. The convenience in use is very im- 

 portant, and it is expected that far more work 

 can be done than with the usual form of in- 

 strument. The images of the stars are not se- 

 riously injured by the two reflections, a result 

 due to the system of mounting the reflectors on 

 flannel sheets. 



The largest and finest heliometer yet made 

 has been brought into activity at the observ- 

 atory of Yale College. One of the first works 

 undertaken by it is the triangulation of the 

 Pleiades by Dr. W. L. Elkin. A yet finer and 

 larger instrument has been contracted for by 

 Director David Gill for the observatory at the 

 Cape of Good Hope, and will probably be com- 

 pleted by the Repsolds during the year 1885. 



Astronomical Work under the Bureau of Navigation, 

 Navy Department. The United States Naval Ob- 

 servatory. The annual report of the Chief of 

 the Bureau of Navigation to the Secretary of 

 the Navy comprises detailed reports of the 

 astronomical work of the Naval Observatory. 

 A board has been organized, consisting of the 

 Superintendent, the senior Professor of Mathe- 

 matics, and the senior line officer, who are to 

 deliberate from time to time upon the conduct 

 of the observatory, and whose conclusions 

 shall form the basis of work to be done in each 

 year. Each officer in charge of a separate 

 branch of work is to submit annually or often- 



