POSITION OF STATION AT HERMITAGE ISLAND. 391 



Lieut. R. HOGGAN'S OPERATIONS at HERMITAGE ISLAND, RODRIGUEZ. 



THE small islet on the south side of the Island of Hodriguez, named on the 

 Admiralty charts Hermitage Island, having been selected for the position 

 of a secondary telescope for observation of the actual Transit of Venus, 

 Lieut. Hoggan, accompanied by Lieut. "W. N. Moore, R.N., of H.M.S. 

 Shearwater, proceeded there on the 30th November 1874, taking with him a 

 4-inch refracting telescope by Dollond, with tripod stand, two sextants, 

 a mercurial artificial horizon with cover, and the two box chronometers 



Hewitt 732 



also the " pocket " chronometer Parkinson and Frodsham No. 4530, beating 

 five times in two seconds. 



Lieuts. Hoggan and Moore remained encamped on the islet until 

 December 10. The errors of the chronometers on local time were determined 

 by a continuous series of observations of equal altitudes of the Sun from 

 December 3 to December 9. At 8 p.m. on December 2, 6, 8, and 9, five 

 rockets were sent up from the summit of Mount Simon (by a party from 

 H.M.S. Shearwater). These rockets were visible from Lieut. Hoggan's and 

 Captain "Wharton's stations as well as from the head station aj; Point Venus. 

 The instants of the bursting of the rockets were noted independently by 

 Lieut. Neate and Mr. Burton at Point Yenus, and by Lieuts. Hoggan and 

 Moore at Hermitage. For various reasons the observations of December 2 

 and 6 were rejected. In the meantime, Captain Wharton connected the 

 station on the islet by a system of triangles with the general survey of the 

 island, as fully described in his Report (page 381). 



From this triangulation the station on Hermitage Islet was 4'. 25"'6 South 

 and O m . 3 9< 59 East of the Altazimuth pier at Point Yenus. The Latitude of 

 Hermitage Station is therefore 19. 44'. 47"'7, and the Longitude 4 h . 13 m . 46 s - 1 

 Bast of Greenwich. 



By comparing the errors of the three chronometers on local mean solar 

 time, as determined from the equal altitudes observed on December 7 and 9, 

 with their errors on Point Yenus mean time, as determined from the well- 

 observed rocket signals on the evening of December 8, the difference of 

 longitude between the two stations appears to be 3 S> 87, a proof of the 



