58 



ASTRONOMICAL PROGRESS AND PHENOMENA. 



whose outside is so burdened that it is a great 

 advantage to be able to utilize the cavity. 

 Through the hole in the declination-axis, the 

 observer is enabled to read the R. A. circle from 

 the eye-end of the instrument. The diameter 

 of the fine-reading circles is three feet. Coarse- 

 reading circles are also provided. Inside and 

 near the top of the column is the driving-clock, 

 which causes the telescope to follow in R. A. 

 the object under observation, by a tangent- wheel 

 five feet in diameter (instead of a sector), which 

 makes the motion continuous. Surrounding 

 the top of the column, and reached by a spiral 

 stairway from its south side, is a balcony, from 

 which an assistant has access to the driving- 

 clock and may control the telescope in all its 

 motions. Here, too, from a certain position, 

 he can read the circles, both coarse and fine. 

 The driving-clock is of the same construction 

 as those used by Messrs. Warner & Swasey on 

 all of their telescopes. It has a double, conical 

 pendulum, isochronously mounted, and the 

 pendulum-balls are at liberty to take their 

 theoretical positions. The observer from the 

 eye-end of the telescope governs all clamps and 

 slow motions by handles within easy reach, and 

 reads both circles without rising from his seat. 

 No observing-chair, commonly so called, will 

 be used, but the entire floor will be raised or 

 lowered by hydraulic machinery, so that, at 

 whatever altitude obssrvations are being made, 

 the observer sits comfortably in his easy-chair, 

 with a table at his side on which lie his obser- 

 vation-book, etc., while the eye-piece is always 

 at a convenient height. The focal length of 

 the telescope is 56 feet 2 inches; and the tube 

 of sheet-steel, 42 inches in diameter, is sus- 

 pended from its center, the point of suspension 

 or center of motion being 36 feet from the 

 floor. The cost of the object-glass was $51,- 

 000; cost of the dome, $56,850; cost of mount- 

 ing, $42,000 ; photographic lens when obtained, 

 $13,000; total, $162,850. When completed, 

 it, together with the unexpended balance of 

 the $700,000 of the original fund, will be turned 

 over by the trustees, of whom Capt. Richard 

 S. Floyd is president, to the regents of the Uni- 

 versity of California, as the astronomical de- 

 partment of that institution, over which Prof. 

 Edward S. Holden, already at the head of the 

 university, will preside. Under the provisions 

 of the trust, the observers are to receive no 

 salaries until the observatory is completed. As 

 the greater dome could not be built until the 

 focal length of the large objective had been as- 

 certained, the delay of several years in secur- 

 ing the two rough disks from Fiel and Sons, 

 of Paris (costing $7,000 each), was greatly 

 deplored. They, now polished, and, in their 

 cells weighing 750 pounds, constitute the visual 

 objective. This instrument is not designed for 

 (and, in fact, is worthless for) celestial photog- 

 raphy, though the attachment to it of a third 

 lens of the proper curves called a photographic 

 lens corrects it for the actinic rays, but renders 

 it useless for the visual. By attaching and de- 



taching this third lens, both purposes are 

 served. The disk received for this lens, con- 

 demned by the Clarks as under a strain from 

 imperfect annealing, and liable to break in the 

 working, was, fortunately for the opticians, at 

 the risk of M. Fiel, who ordered the work to 

 proceed. As predicted, the lens, during the 

 process of grinding, broke into three pieces, 

 entailing heavy loss. The photographic lens 

 must, by consequence, be delayed for an indefi- 

 nite time, greatly to the regret of the director, 

 who desired early to bring the great telescope 

 into photographic work. The Lick Observa- 

 tory is on the summit of the lowest of the three 

 peaks of Mount Hamilton, of the Coast Range of 

 California, 4,285 feet above the level of the sea, 

 50 miles south of San Francisco, and, in an 

 air-line, about 40 miles from the Pacific Ocean. 

 The site was chosen by the gentleman whose 

 name it bears, and whose tomb, as well as monu- 

 ment, it is to be, James Lick, who died in 1876. 

 The advantages of this situation can not be 

 overestimated. Prof. Holden assures us that, 

 for six or seven months of the year, every night 

 is clear, while of the remainder, half the nights 

 are good for observation. The instruments 

 now mounted are a 12^-inch and a 6-inch equa- 

 torial, a comet-seeker, a 4-inch transit, a 6- 

 inch meridian circle, a Repsold vertical circle, 

 a photo-heliograph, and a heliostat. In addi- 

 tion, there are five clocks, mean time and si- 

 dereal, and several chronometers. A carriage- 

 road, very circuitous but of easy grade, twenty 

 miles long, has been constructed at great ex- 

 pense by the county of Santa Clara to the ob- 

 servatory, which obviates the difficulty of as- 

 cent and affords a charming drive. 



Floating Dome. The new observatory at Nice, 

 France, has a dome possessing at least one 

 novel and apparently valuable feature. The 

 bottom of the dome is provided with a circular 

 float, which revolves in a narrow annular tank 

 filled with a solution of chloride of magnesium 

 in water. It is a little heavier than water, 

 and will not freeze until a temperature of 40 

 centigrade below zero is reached. Running 

 wheels are also used, but the pressure on them 

 is slight, and it may be entirely removed by the 

 addition of more water to the tank. Guide- 

 wheels prevent the dome from swaying later- 

 ally. The practical working of the great dome 

 of steel, seventy-two feet in diameter and 

 weighing 95 tons, is quite satisfactory. The 

 telescope, a refractor of thirty inches aperture, 

 has now been in use for several months. The 

 object-glass was made by the Henry Brothers 

 of Paris. 



Star-Catalogues. A valuable acquisition to our 

 stock of star-catalogues has just been issued, 

 known as the " Second Armagh Catalogue." 

 It comprises 3,300 stars, mostly Bailey's, re- 

 duced to the epoch of 1875. The observations 

 were made by the late Dr. Robinson, and pre- 

 pared for publication by his successor, Dr. 

 J. L. E. Dreyer. The first four hours of 

 the " Edinburgh Catalogue," constituting vol. 



