475 



ESTABLISHMENT AT THUMB PEAK. 



On the morning of 1874, December 7, civil reckoning, Lieut. Somerville 

 Goodridge, R.N., accompanied by the Rev. A. B. Eaton (Naturalist of the 

 Expedition) and servants, proceeded in the Supply from Observatory Bay 

 towards Thumb Peak, and selected a spot at which the observation of the 

 transit could be made. The party then went in the Supply to the anchorage 

 at Three Islands Harbour, for the night ; and returned early in the morning 

 of December 8 to the selected spot, and prepared for the observation. They 

 encamped there for the night. 



The locality is fixed by the following bearings : 



S.E. part of Thumb Peak, S. 75. 20'. W. 

 S.E. point of Sughin Island, N. 19. 20'. E. 

 S.E. point of Sharban Island, S. 62. 00'. E. 



It is believed that these bearings are magnetic, uncorrected for Magnetic 

 Variation. 



For determination of the co-ordinates of the station in the usual form, 

 Mr. Perry, on December 13, four days after the Transit, proceeded in the 

 Supply to Thumb Peak, carrying with him De la Rue's Altazimuth and a 

 sidereal chronometer called S, and returning on December 21. On a small 

 hill, 215 feet high, near Lieut. Goodridge's station, a pile of stones was built 

 for the altazimuth, and a tent placed over it. Mr. Perry observed stars near 

 the meridian for latitude, and Sun and stars in other positions for chrono- 

 meter-error. The chronometer was compared with Z of the Supply when she 

 made the rounds mentioned in the last section ; and from these comparisons, 

 and those made before starting and after returning, the relation of its times 

 to the local times at Observatory Bay was found. It will be seen shortly 

 that no extreme accuracy is required in this process ; and I have therefore 

 thought it unnecessary to exhibit all the details. The result was, that the 

 latitude of the station is 49. 31'. 11". South, and that in longitude the station 

 is l m . 7 S '7 East of Observatory Bay, or 4 h . 40'". 4P-2 East of Greenwich. 



The telescope used by Lieut. Goodridge is an achromatic by Dollond, of 

 3^r inches aperture and 46 inches focal length, on a firm tripod stand, with 

 horizontal and vertical movements ; lent from the Cambridge Observatory. 

 It was not fitted with a diagonal reflector for feeble reflection of the Sun's 

 rays ; dark glasses were screwed on the eye-hole as required. 



