250 Prof. Encke on the Construction and Arrangement 



kindness to communicate to me. The columns of the time of 

 transit and semidiameter of the sun are taken from BesseFs 

 tables. The calculations have been most rigorously executed, 

 and the latitude has been duly taken into consideration in the 

 right ascensions and declinations. We may therefore hope, 

 that, should even new tables of the sun be published before 

 1830, the calculated positions will not greatly deviate from the 

 true ones. 



The following four pages III — VI. contain the positions of 

 the moon. The odd ones III. and V. contain the longitude 

 and latitude, and the right ascension and declination, of the 

 moon for every mean noon and midnight at Berlin. The 

 present arrangement of these columns, in which the data fbt 

 noon are not separated from those for midnight, as was hitherto 

 usually done, appeared to be more convenient for taking the 

 differences. On the opposite pages IV. and VI. are contained 

 in the first place for the same epochs the horizontal equatorial 

 parallax of the moon which supplies the place of the distance, 

 and the diameter as seen from the centre of the earth. Next 

 follow the three columns which refer to the moment of the 

 moon's culmination at Berlin ; viz. the mean time of the moon's 

 superior or inferior culmination, with the right ascension and 

 declination corresponding to that moment, likewise referred 

 to the centre of the earth. The upper and lower culminations 

 are distinguished by the letters O and U. 



The two last columns give the times of the sun and moon's 

 rising and setting, designated by the letters A and U. Below 

 the odd pages III. and V. are placed the changes of the moon 

 by mean time; below the even* ones, the times of perigee and 

 apogee. 



The columns contained on the even pages are intended to 

 facilitate the calculation of the apparent place affected by 

 parallax; this will be treated of more in detail in another 

 place. For this reason the apparently misplaced times of the 

 sun's setting have been here inserted. Those times have be- 

 sides for astronomers no other essential importance, except as 

 far as the visibility of other heavenly bodies is dependent on 

 them. The moments of the sun and moon's setting are, as always 

 where there is no particular mention, given in mean time. 



All the calculations for the moon have been deduced from 

 Burckhardt's tables, from which the later ones of Damoiseau 

 do not appear ever to deviate considerably. The accuracy of 

 the tables of Burckhardt having been much confirmed of late 

 years (in the opinion of a very competent judge), they have as 

 yet been preferred to the others founded more on theory. 



For the careful execution of this portion of the work, I am 



indebted 



