150 RECORD OF SCIENCE FOR 1886. 



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

 Mount Haniilton ou December 27, 1880, and have been packed away 

 in a fire-proof vault in readiuess for the mounting. 



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

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

 Clarks found that the first piece of glnss sent them fortius lens showed 

 signs of internal strain due to insufficient aniu^aling, and the work of 

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

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

 three ])iec('S while upon the grinding tool. Another disk will be ])ro- 

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

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

 to this. The recent death of Feil p^re may cause serious delay in ob. 

 taining the glass for the third lens. 



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

 Swas<\v, of Cleveland, Ohio, and will be delivered at Mount Hamilton 

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

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

 the tight 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 $50,800. The question 

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

 ing the floor vertically 10 feet. Some such arrangement becomes ab- 

 solutely necessary when we consider that the " spectroscoi)ic length" 

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

 photographic length some 8 feet less; the eyei)iece 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 parallel motion, by hydraulic rams. The 

 cost of the floor will be $14,500. 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 

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



In the Slimmer of 1880 Prof. G. C. Comstock made an investigation 

 of the Pepsold meridian circle and a preliminary determination of the 

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

 the longitude given by the U. S. Coast Survey is 8'* 0'" 34'*.35 west of 

 Greenwich. A time servic-e 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 HohhMi's ])lan for utilizing to tlie utmost the magnificent 

 equipment under his chargcniust commend itself to everyone. The 

 plan is to relinquish the use of the 3C-iuch equatorial for certain hours 



