.^38 . .'.-^ . A NEW METHOD OP 



which the Solar and Lunar Tables have attained, scarcely leaves a desideratum 

 on this head. It is true, that several equations in the Lunar theory, still re- 

 main unknown, but there is every reason to believe, that the amount of error 

 which is superinduced fi'om the omission of these equations, will not, for many 

 years to come, involve any perceptible error in the Lunar Tables. The 

 accuracy of the Lunar and Solar Tables being thus established, and the moon's 

 motion, in right ascension, being more rapid than that of the other planets, it is 

 evident that the determination of Iier position in the heavens, at any instant of 

 time, under any meridian, must afford the readiest, and one of the most accurate 

 methods of determining the difference of longitude between that meridian 

 and any other, for which the moon's place has been computed. This object 

 may be attained in two ways— one of which is by observing the interval that 

 elapses between the transit of the moon's limb, and of one or more stars,* 

 whose right ascensions are well determined. 



From a comparison of the results deduced from this method, and that of 

 theeclipses of Jupiter's satellites, it has been found, that the longitude deduc- 

 ed from the latter, is generally in excess of that deduced from the lunar tran- 

 sits. This remark is grounded on my own experience, but I should not have 

 hazarded it, had not other observers drawn the same conclusion. It may, 

 perhaps, be difficult to point out the sources of error in either. This much, 

 however, may be said, that the data from which the Lunar Tables are construct- 

 ed, (excepting, of course, the errors of computation,) are as correct as theory, 

 combined with observation, can make them, and that the right ascensions of 

 the stars, which may be selected, for comparison, from Pond's Catalogue, have 

 no error that is likely to come within the range of ordinary observation, or 



* The other method alluded to, will form the subject of a separate Essay. It is as accurate 

 as that of the Transit Instrument. 



