On the Determination of tlie Errors of tlie Cape Reseau, 



Gautier No. 8. 

 r.y David Gill and Harold Jacoby. 



The present investigation lias becn carried ont in a manner similar to 

 Dr. Gill's investigation of the Oxford reseau (Meni. R. A. S. Vol. 51). The 

 methods employed hâve, however, been considerably extended. The straight- 

 ness of each line has becn separately tested, and the source of error found 

 by Donner (Acta Soc. Sei. Fennicae, Tome XXI N:o 8) to be peculiar to the 

 Repsold measuring machine, and called by him „projection error", has been 

 investigated for the Cape machine. Ali the observations hâve been made by 

 Messrs. Woods and Goodman, under our joint supervision. The formnlae 

 of réduction and the préparation of the paper for the press are due to Mr. 

 Jacoby. 



It is uunecessary hère to describe the Repsold measuring machine of the 

 Cape Observatory. It is similar to the Leiden instrument, which has been 

 figured and described by BAKHuvzen (Bull. Com. Perm. Tome I, p. 169.). 

 Throughout the entire operation every care was taken to eliminate the effects 

 of température changes, by means of symmetrical repetition of the observations 

 in the reverse order. Error of runs, and periodic errors of the micrometcr 

 screws have also been eliminated. Every set of observations was independently 

 made by the two observer?, in such a way that each observer's results are 

 complète in themselves. 



