390 ON THE MEAN PLACES OP 84 FUNDAMENTAL STARS. [48 



ON A PROPOSED NEW FUNDAMENTAL CATALOGUE. 



I have frequently felt great inconvenience from the changes which have 

 been made from time to time, in the Fundamental places of the Standard 

 Stars in the Nautical Almanac. At present, also, different astronomers use 

 different Fundamental places, so that it is impossible accurately to compare 

 the observations made at different observatories, or at the same observatory 

 in different years, without a troublesome preliminary investigation of the mean 

 differences of the several catalogues employed to determine the Clock error. 



The appearance of the Greenwich Twelve-year Catalogue seems to me 

 to afford an excellent opportunity for the formation of such a catalogue as 

 astronomers in general would be likely to employ in the reduction of their 

 observations. By comparing the places in the Greenwich Catalogue with 

 those of Bradley given in Bessel's Fundamenta, places would be obtained, 

 which for many years to come, might be more depended on, than those 

 given by a year or two's observations, however near these might be to the 

 time for which the places were wanted. In order, however, to ensure this 

 general assent of astronomers and to do justice to the excellence of the 

 materials, the most scrupulous accuracy should be attended to in the 

 reduction of the places to the proposed epoch, and in the calculation of 

 the coefficients of the 1st and 2nd powers of the time which are required 

 and wanted in order to find the places for any other epoch. 



A short Appendix should be added to the Nautical Almanac in which 

 the proposed Catalogue is given, fully explaining the method employed in 

 its formation, in order that astronomers might use it with confidence. 



I .proceed to point out the method which it appears to me most 

 desirable to adopt for this purpose. 



The R.A. for 1840 and 1845 given in the Greenwich Catalogue are not 

 referred to the same Fundamental position of the Equinox. 



The mean corrections of the R.A. of the Fundamental Catalogue in 

 the Nautical Almanac for 1834, given by the observations of the first 6 

 years and of the last 6 years, differ by 8 '067. Part of this difference, 

 however, arises from the proper motions having been omitted, except in a 

 few cases, in the Nautical Almanac Catalogue, so that the mean corrections 

 would vary with the time. By the comparison of the R.A. for 1840 and 

 1845, of the 30 stars common to the Greenwich Clock List and the Tabula 

 RegiomontancB, using as a basis Bradley 's places for 1755, I find that in 



