196 SCIENTIFIC RECORD FOR 1884. 



■w^ork complete; a photographic leus with accessories for celestial 

 photograpliy ; two micrometers for measuring double stars; four mi- 

 crometers for measuring star plates ; a transit instrument by Stackpole 

 & Brother ; a sidereal clock, and additional appliances for the observa- 

 tory. Mr. Eutherford generously bears the expense of moving and of 

 remounting the instruments. 



Observatory of the University of Virginia. — Messrs. Warner and Swa- 

 sey, of Cleveland, Ohio, have completed the great dome for the new 

 McCormick Observatory at the University of Virginia. It is hemis- 

 pherical in shape and is 45 feet in diameter, and a personal inspection 

 has convinced the writer of its excellent qualities. 



It can be revolved 300° in 80% by a pull of 15 pounds on a rope. The 

 direct pressure required to move it is 45 pounds. The three shutters 

 can be opened in 20% by a pull of about 10 pounds. 



Willets Point. — A very interesting report is published by General H. 

 L. Abbot, of the Corps of Engineers, U. S. Army, on the astronomical 

 work which has been done during 1884 at the engineer post of Willets 

 Point, New York Harbor. It is to this school of apj^licatiou that young 

 ofiicers of engineers are sent io learn the practical application of their 

 studies at West Point. They are taught the ])ractice of military sur- 

 veying, mining, torpedo service, etc., and also the application of astron- 

 omy to military and boundary surveys. Each year a general order is 

 issued, giving the results of the past year's work in practical astron- 

 omy. The order for 1884 may be summarized as follows: 



Each officer makes a long series of determinations of local time with 

 various instruments, and in various ways. With the portable transit, 

 the time of transit is at first recorded by an assistant, at the word given 

 by the observer; next, the observer records his own time by the relay 

 heat of a chronometer every 1 second ; next by the chronograpliic method, 

 and lastly hy the beat of the chronometer itself (ever^- 0.5 second). Be- 

 ginners use these methods in succession in the order named. 



Personal equation is studied by means of Eastman's machine (see 

 Wash. Ast. Obs, 1875). 



The time determinations are given for each day of observation, with 

 the probable errors. 



Time determinations by sextant observations are also given, and by 

 means of the (known) correction of the standard chronometer the error 

 of each observation and observer is determined. 



We quote below the errors of the sextant clock cori'ections so deter- 

 mined. (Usually 10 altitudes of an east star and 10 of a west were em- 

 ployed). 3«.0; 3.8; 2.0; 1.2; G.5; 1.8; 1.9; 0.0; 0.7; 0.1; 0.9; 1.0. 



Observations for latitude weie made by the sextant and by zenith 

 •telescopes. With the sextant the errors in seconds of arc were as 

 follows (l"=101feet): G".9; 4".3; 2".2; 7".4; 1".7; 1.5; 10".4. 



A table of the separate latitudes obtained by eaclj observer, with 



