LONGITUDE OF MOKATTAM. 



273 



The lines in the preceding table show the division into the groups from 

 which the following mean errors of Reid and Sons 1207 are obtained. 



TABLE V. MEAN ERRORS and RATES of the Chronometer REID AND SONS 1207 

 (Sidereal) deduced from the Comparisons (at PORTHCUKNO) with the 

 Chronometer C. FRODSHAM 3205 (Mean Solar). 



The results (a), (c), (e), and (g) are obtained from comparisons with the 

 chronometer C. Frodsham 3205 made near to times of determination of 

 the error of the latter by the exchange of galvanic signals with Greenwich ; 

 they may, therefore, be adopted as fundamental determinations of the error 

 of Reid and Sons 1207. 



The results (b), (d), (/), and (h) depend upon a " chronometer slow " of 

 C. Frodsham 3205, inferred from the fundamental errors of that chronometer 

 given in Table III. ; they are, therefore, affected with any possible irregularity 

 of rate of that chronometer. The results (i) and (k) are inferred from those 



