LONGITUDE OF EL PASO, FRONTERA, AND SAN ELCEARIO. 



141 



' The coincidence between these differences is satisfactory. The computations were made hy 

 independent computers: the first, hy Assistant J. H. Clark; tlie Becond, by Asgistjuifc J. 



The observations for the first were made by myself; those at San Elceario by 



O'Donoghue. 



Lieutenant W. F. Smith. 



To give greater effect to the results, and to establish beyond the probability of future change 

 the longitude of Frontera — which is about the longitude of the middle of the continent, and is 

 a primary station on the survey of the boundary — an attempt was made to connect tlie obser- 

 vatory of San Elceario with that of Frontera by flashes of gunpowder, and the following is the 

 result. It should be observed that the Frontera here mentioned is not the Frontera of tbc old 

 maps of North America. Frontera signifies a frontier town, but in this instance is the name 

 given by its proprietor to a newly-constructed hut, built immediately on the ratification of the 

 treaty of Guadalupe Hidalgo, at a point some eight miles above El Paso, where it was sup- 

 posed the boundary under that treaty would leave the Eio Bravo. The difference of longitude 

 between Frontera and San Elceario, observed by flashes on the nights of the 14th, 18th, lOtli 

 February, and 14th March, 1852, was found to be as follows: 





Date. 



1 



No. of observat'ns 

 each night. 



Diff. of long., El Paso, ' 

 east of Frontera. 



No. of obscrvat'ns 

 each night. 



DilT. of long., f>an Klre- 



ario, cast of Frontera. 



February 14 - ^ 



1852. 



14 

 15 

 12 



12 



r 



s. 



16.03 

 16,06 

 15.84 

 15.84 



13 



15 

 15 



1 



VI, s. 



1 7.16 



18 



1 7. 54 



19 



1 7.36 



March 14 -^ - -- 



1 7.15 











Mean of 53 observations 15. 94 



Mean of 57 observations — 1 < . 30 



The difierence of longitude by observations on the moon and moon culminating stars is l" 

 08'.58, which acrrees with that determined by flashes within 1'.3. Now, assuming the difference 



determined by flashes as correct, and giving equal weight to the observations at each station 

 the longitude of Frontera will be diminished by 0'.65, and that of San Elceario will be increased 

 by the same quantity ; so that the final result will be : 



Frontera, west of Greenwich 

 San Elceario '' " 



y"" 06" 12'.33 

 7 05 04'.95 



05™ 56'.39. 



The longitude of the observatory at El Paso erected by the Mexican commission, two hundred 

 feet south and five hundred feet west of the Cathedral tower, was determined by flashes observed 

 simultaneously by Senor Salazar and myself on the nights stated in th^e pre^cedmgjart of this 

 article, to be 15'.94 east of Frontera ; hence the longitude of EI Paso, T 



A discussion of the longitudes of the Presidio del Norte and of Eagle Pass, on the Eio 

 Grande, shows a difl-erence between the longitude obtained by using the Greenwich Ephemeris 

 and that obtained by using the corresponding observations at Greenwich, to be in the first case 

 + 19% and in the second + l^M. Comparing these with the same quantities obtamed at 

 Frontera and San Elceario, made in the same year, it will be seen that there is a comcidence, 

 sho 



wmg that in this case the error in the predicted place of the moon is nearly uniform for the 



same year. 



The difference between the longitudes obtained in 1849, those computed from data in the 



