98 



The Bev. S. J. Perry on 



[Mar. 22, 



Station. 



H. F. 



V. P. 



T. F. 



^ ^ J 





34559 

 3-4567 

 3-4547 

 6 34y4 

 34615 

 3-4510 

 3-4501 

 3-4502 



10-6852 

 10-6876 

 10-5884 

 y 7278 

 10-5986 

 10-5665 

 10-5952 

 10-5816 



11-2327 

 11-2353 

 11-1378 



10- 2883 



11- 1496 

 11-1158 

 11-1428 

 11-1299 



If, now, we combine each determination of the horizontal force with the 

 mean value of the dip for December and January, we obtain the following 

 results at Observatory Bay for the Vertical Force and the Total In- 

 tensity : — 



V. F. 



T. F. 



10-5991 



11-1483 



10-6015 



11-1509 



10-5954 



11-1444 



10-6163 



11-1663 



10-5841 



11-1325 



10-5813 



11-1296 



10-5816 



11-1299 



The probable error of the mean value of the intensity is thus reduced 

 from +0-0126 to +0-0035; we may therefore consider 11-1431 as the 

 adopted value of the total force for January 1st, 1875. 



The Magnetic Declination. 

 The advantage of a fixed observatory enabled us to determine with 

 great exactness the direction of the astronomical meridian, and to connect 

 the position of the magnetic pier with the sites of the astronomical instru- 

 ments. On January 28th and on February 5th observations of the sun 

 were taken with an excellent transit theodolite made expressly for the 

 expedition by Messrs. Troughton and Simms. The results give the 

 following values for the azimuth of a well-defined point on the Prince of 

 Wales's Foreland, some ten miles distant : — 



Circle right. Circle left. 



January 28th 95 17 10 



February 5th .. 95 19 30-5 



95 18 27 

 95 18 18 



95 18 20-25 95 18 22-5 



The resulting azimuth of the Foreland would therefore be 95° 18' 21"*38 

 E. ol the north point. The correctness of this angle, on which all the 

 declinations depend, was tested by a series of measurements connecting 

 the azimuth of the Foreland (F) with the azimuth mark (m) of the great 

 theodolite, a most accurate instrument, especially designed by Sir G-. B. 

 Airy for the lunar longitude observations at Kerguelen. As the Fore- 



