150 RECORD OF SCIENCE FOR 1886. 



The crown and flint lenses for the 30-inch objective arrived safely at 

 Mount Hiunilton on December 27, 18S6, and have been packed away 

 in a fire-proof vaidt in readiness for the mounting. 



It is tlie intention to provide three lenses, the third a " photographic 

 corrector" which can be slipped on in front of the other two. The 

 Chirks found that the first piece of glass sent them for this lens showed 

 signs of internal strain due to insufficient annealing, and the work of 

 figuring was only undertaken at the risk of the makers, Feil & Co. 

 The suspicion of strain proved well founded, for the disk burst into 

 three i)ieces while upon the grinding tool. Another disk will be pro- 

 cured and should be rcadj' by June 1, 1887. The cost of the objective 

 was $52,000. The photographic lens will add several thousand dollars 

 to tliis. The recent death of Feil pere may cause serious delay in ob- 

 taining the glass for the third lens. 



The mounting is under way in the workshops of Messrs. Warner & 

 Swasey, of Cleveland, Ohio, and will be delivered at Mount Hamilton 

 in June, 1887, for $42,000. It will contain many novel devices, among 

 them an application of a modified form of the bicycle ball-bearings to 

 the light ascension and declination axes, which will insure great ease 

 of movement. The driving clock will have an electrical control. 



The hemispherical dome of 70 feet interior diameter has been built 

 by the Union Iron Works, of San Francisco, for $56,800. The question 

 of an observing chair has been met by adopting Grubb's plan of mov- 

 ing the floor vertically 16 feet. Some such arrangement becomes ab- 

 solutely necessary when we consider that the "spectroscopic length" 

 of the telescope is some 5 feet more than the visual length, and the 

 photographic length some 8 feet less; the eye-piece may be 7 feet from 

 the base of the dome when the telescope is pointed to the zenith, or it 

 may be .35 feet in the horizontal position. The floor will be raised in 

 four minutes with a perfectly ])arallel motion, by hydraulic rams. The 

 cost of the floor will be $11,500. A star spectroscope is to be made by 

 Brashear, of Pittsburgh, for $1,000, and the micrometer by Fauth, of 

 Washington, for $750. 



The total cost of the observatory will be a little over $500,000, leav- 

 ing nearly $200,000 available as a permanent endowment. The annual 

 income of the observatory from all sources will be about $20,000. 



In the summer of 1886 Prof. G. C. Comstock made an investigation 

 of the Repsold meridian circle and a preliminary <leterm!nation of the 

 latitude. The resulting latitude of the north dome is + 37° 20' 25". 2 ; 

 the longitude given by the U. S. Coast Survey is 8'' 6'" 34'' 35 west of 

 Greenwich. A time-service is in operation over the whole Pacific sys- 

 tem of railways from Ogden to El Paso. Volume 1 of the observatory 

 publications is in press, and will be distributed in the early summer. 



Professor Holden's plan for ntilizing to the utmost the magnificent 

 equipment under his charge must commend itself to every one. The 

 plan is to relinquish the use of the 36-iuch equatorial for certain hours 



