POSITION OF STATION AT POINT COTON. 381 



REPORT of COMMANDER W. J. L. WHARTON, R.N., on the POSITIONS of the 

 SECONDARY OBSERVING STATIONS in RODRIGUEZ and on his own OBSERVATIONS 

 of the TRANSIT of VENUS, December 8, 1874.* 



1. POSITIONS of the SECONDARY OBSERVING STATIONS. 



These positions were determined by triangulation from the primary station 

 at Point Venus. 



A base line of 2,503 feet, situated on the flat sand-covered coral reef, was 

 measured, at low water, six times by means of two chains. The greatest 

 difference was 2 feet. 



This base was expanded by five well-proportioned and carefully observed 

 triangles to 9882'3 feet, and from this last base three systems of triangles 

 were started, all of which terminated at the Hermitage Islet, and one system 

 terminating at Point Coton. 



The theodolites employed had Azimuth circles of 8, 7, and 5 inches. No 

 triangle was accepted the sum of whose angles differed more than 1' from 

 180. From the conformation of the island some ill-conditioned triangles 

 were unavoidably admitted into the system, but the small angle was invariably 

 at one of the known stations. To this circumstance, however, a part of the 

 discrepancy in the result is due ; but as the first system, although the best 

 in point of number and in the forms of the triangles, entailed longer dis- 

 tances than could be accurately measured by the power of the small 

 theodolites, the arithmetical mean of the three results for Hermitage Islet 

 has been taken. From this point 12 true bearings were taken which differed 

 1^' among themselves. 



The following are the results : 



Distance of the station on Hermitage Islet (marked H on the Survey Plan) from the station 

 (marked S) at Point Venus 



By the first system, 6 triangles, 26835-6 feet South, 621 3-4 feet East. 

 By the second system, 6 triangles, 26824-9 ,, ., 5z3o - 5 

 By the third system, 12 triangles, 26845-1 52i5'8 



Mean 26835-2 ,, 5220-0 



* The details of Commander Wharton's surveying operations in the Island of Rodriguez are 

 deposited in the Hydrographic Department at the Admiralty. 



3 c 2 



