( 6(^2 ) 



differences between tlie results from the photographs and tliose tVoni the 

 helionrieter in 1902. Accordingly I have rejected all the i-esults from 

 the photographic series, witli the exception of /v, and ^y, , which dei)end 

 almost exclusively on differences of declination, in which the nnknovvns 

 hhi, Aki, A^Vi have small and not constant coefficients, and the 

 elimination of di), is therefore much more complete. I have adopted 

 the values derived from the solution in which the orientation was 

 determined from the traik. The reason why this is to be preferred 

 to the orientation derived from the standard stars has been explained 

 by me in Cape XII. 3, Appendiv. The values of Lqi and Lpi have 

 been adopted unaltered from Cape XII. 4. 



6. Photographic plates taken at the observatories of Helsingsfors 

 by Prof. DoNNER and of Pulkowa by Dr. Kostinsky, measured by 

 Renz, and published in the Mémoires de St. Petersbourg, VHP'' series, 

 Vol. VII, W. 4 and Vol. XIII, N«. 1. 



From the measures by Renz I liave derived corrections A/j, A^, 

 A 4 to the mean longitudes, which have been published in Gron. 

 Publ. 17. The values found there have been adopted unaltered. 



Renz measured the positions of the satellites relati\ely to Jupiter. 

 I have commenced my discussion of these measures by rigorously 

 eliminating the, pointing on the planet. It appears that these pointings 

 are indeed subject to very large systematic errors (Gron. Publ. 17, 

 art. U). 



7. Heliometer observations made by Bessel in Königsberg from 

 1832 to 1839, published by himself in "Astronomische Untersuchun- 

 gen, Band IF'; re-i-educed by Schuk and published in Xova Acta Acad. 

 Leop. Carol., Vol. 44, pages 101 — 180. Only the values of /^ 3, ^3, A^, 

 k^ are included in the discussion, and only ]i^ and k^ lia\e contri- 

 buted to the final result. 



Bessel has referred the satellites to the planet. His observations 

 are affected by large systematic errors, as has been pointed out by 

 ScHUK, in consequence of which their real accuracy cannot be assumed 

 to be in accordance with the jirobable errors. 



8. The values of the "own" jiodes and perijoves in 1750. These 

 have been determined by Delambre and by Damoiseau. Regarding the 

 accurac}' of these determinations nothing definite is known. The agree- 

 ment between the two results, which is very good, cannot be taken 

 as a measure of the accuracy, since we do not know in how far 

 Damoiseau is independent of his predecessor. It will be seen below 

 tiiat the role played by these data in tlie derivation of the final 

 results is a very subordinate one. 



If from a combination of the values found on different epochs for 



