140 



ASTRO^'OMY. 



observed. 



mode of obtaining 



of longitude to many other stations ; but in a country without settlements, and traversed by 

 bands of savages who kill at sight, it was impossible to do so, as every j^avty that went out had 

 to be escorted by ten or fifteen armed men. 



Where neither of the above means could be resorted to, longitude was obtained by transmis- 

 sion of chronometers from some established point. This method, so successful at sea, where 

 the motion is uniform and smooth, has objections on land, principally the impossibility of 

 moving chronometers without deranging the rate. Every method of transporting them was 

 tried— on carriages, on foot, and on horseback ; and an ordinary spring-carriage was found to 



minm 



be the best. Ko test can be applied to check an error in dete 

 mission of chronometers ; for even with three chronometers it is possible for all to be affected 

 in the same Avay, though of course not in the same degree— that is to say, all may run, while 

 travelling, too fast or too slow ; and when you halt, may resume their former rates. 



The observations at the two stations 11 and 12— Frontera and San Elceario— being about the 

 centre of the continent, and in a geographical point of view more important than any others, 

 were combined to arrive at the results given. 



om 



_ ^liJ.V/U_ 



lunations, computed from the predicted place of the moon and moon cul- 



minatin 



The same, after applying the correction due for corresponding observations 



t" OS'^SS'.S 



from 



place, is 



For the 1st lunation, December and January, 1851-'52 7 06 11.38 



2d " January and February, 1852 13.34 



3d " February and March, " 14.73 



4th " March and April, " 12.48 



Mean 



Difference due to correction 



7 06 12.98 

 -t- 17.68 



The longitude of San Elceario deduced from observations on forty moon cul- 

 minations^ extending through three lunations, computed from the predicted 

 place of the moon and moon culminating stars, given in the Greenwich 

 Ephemeris for 1852 , 



The same^ after applying the correction due for corresponding observations 

 made at Greenwich, is — ■ 



For the 1st lunation-, January and February, 1852 7 05 02.52 



2d " February and March, " 04.31 



7'' 04"46'.55 



3d " April, 



£C 



03.44 



Mean 



7 05 03.42 



By combining these observations with corresponding ones at Cambridge, 

 Mass., we get 



Difference due to correction 



7 05 04.3 

 + 17.75 



