204 



ASTRONOMY. 



TABLE VII. 



Tahidation of results for Imgitude of astronomical station at Ringgold harracTcSj derived from 

 ohscrvaiions made ivith 30-incJi transit {maker iinhnoivn) and sidereal chronometer No. 2440, 

 (J}tj ParJdnson d Frodsham:) By Major JV. H. Emory, Chief Astronomer and Surveyor oj 

 United States and Mexican hoitndary survey, assisted by G. (7. Gardner and J. H. Clarh. 



Date. 



Authority for elements used 



Moon's limb observed. Resulting longitude. 



1853. 



June 17 



18 

 20 



95 



July M 



15 

 16 

 18 



Greenwich observations 



Philadelphia Iliyb School 

 ....do -,..do 



First 



do 



Greenwich observations 



do 

 do 

 do 



do 



do 

 do 



Second 



do 



First 



Philadelphia High School 



do. 

 do 

 do 



h. 171-. S, 



6 35 05.90 

 03.42 

 03.36 

 08.39 

 02.61 

 10.49 

 07.41 



07,98 



Longitude of Ringgold barracks = 6A. ^5m. 06s, 19. 



Discussion of the longitude of astronomical station (g) near the mouth of the Bio Bravo del No7ie. 



OFricE OF Survey of United States axd Mexican Boundary, 



Washington, D. (7., February 9, 1856. 



Sir: In presenting to you the final results of the computations for the longitude of the astro- 

 noaiical station estahlished under your direction in 1853, near the mouth of Kio Bravo del 

 Korte, I have heen delayed for want of all the corresponding moon culminations observed at 

 Greenwich throughout the four lunations. 



The observations which were commenced by yourself and continued by Messrs. G. C. Gardner 

 and J. H. Clarlc, extend through four lunations, commencing August 12, and ending November 



22, 1853. 



M 



Thorn from corresponding observations at Greenwich observatory, furnished in manuscript, in 

 1853, by Professor Airy, astronomer royal, as well as from the corresponding observations made 

 at Philadelphia High School observatory during the same period — giving for the position of the 

 astronomical station, in longitude, 6A. 28m. 30^.5 west from Greenwich observatory. 



Having recently received the printed observations of 1853, made at Greenwich and Eadcliffe 

 observatories, the observations of the fourth lunation have also been computed by Mr. Thom, 

 and the results combined with those previously deduced from the first three lunations, without 

 producing any change in the result hitherto adopted, as above given. 



The instruments used at this station were a 46-inch transit, made by Troughton & Simms, 

 of London, and an excellent sidereal box-chronometer, made by Parkinson & Frodsham. 

 The transit was mounted on a massive brass stand, which rested on a pine log, imbedded about 

 eight feet in the sand, the whole sheltered by a temporary wooden structure. 



The accompanying tables, marked A, exhibit all the observations in detail, with the corrections 

 for instrumental errors as applied, together with the several results deduced from the observa- 

 tions of each night. The tables marked B, C, D, exhibit the computations of those instrumental 

 errors, with their adopted results^, as follows: 



^ 



1. The computed values of the equatorial intervals of each wire from the middle wire • ih.' 



illumination being east 



are (see table B) : 



