698 TERRESTRIAL MAGNETISM, 



between 4 and 5 o'clock in the afternoon, so as to correspond with 

 the times of observations at Gottingen. Each set of observations 

 extends over 24 hours, and the times of observations are given in 

 the tables, beginning at 4h. 37m. 34s. mean Fern Rock time, i.e, 

 at 10 p.m. Gottingen time, the difference of longitude being 

 assumed to be equal to 5h. 22m. 26s. 



The winter quarters at Van Rensselaer Harbour were in lati- 

 tude 78° 37' N. and longitude 70° 40' W. The Observatory was 

 of stone, 10 feet square, with a Avooden floor and roof, and with a 

 copper fire-grate. 



The results of the observations of chauges of magnetic declina- 

 tion as given in the tables show that the total easterly deflection 

 is greatest at 2 a.m., when it is equal to 29', and the greatest 

 westerly deflection, which amounts to 37'*8, occurs at 12 noon, 

 the needle being in its mean position about 6*45 p.m. and 

 7 a.m. 



The observations for changes of magnetic declination at Fern 

 Rock have been compared with those at Greenwich and Washing- 

 ton, and the results of these comparisons are given in the tables. 



7. Magnetic Observations in the Arctic Seas, by Dr. Hayes, 

 at Port Foulke, in 1860-61. (" Smithsonian Contributions, 

 vol. XV., p. 42.) 



The Observatory was erected on the first of a series of terraces 

 which lay north-east from the anchorage, and its foundation 

 was 38 feet above the mean tidal level. The rock on which it 

 stood was a dark reddish-brown syenite, which rose on either side 

 of the harbour into hills from 600 to 800 feet high. It faced 

 the S.W., its axis being nearly in the magnetic meridian. 



Winter quarters in Port Foulke were in latitude 78° 17' 39" 

 and longitude 73° 0' 0" west of Greenwich, 20 miles south of the 

 latitude of Rensselaer Harbour, and distant from it by the coast- 

 line about 55 miles. 



The unifilar magnetometer was mounted in the centre of a room 

 8 feet square and 7 feet high, on a stand made of two kegs, whose 

 heads being removed, and the ends carefully fitted together, were 

 filled with beans and water ; the lower keg was placed on the 

 solid rock through a hole cut in the floor. 



For diurnal variation of magnetic declination, hourly observa- 

 tions were recorded on 15 days between November 26, 1860, and 

 March 4, 1861, at intervals of from six to eight days. 



The diurnal variations at Port Foulke and Van Rensselaer 

 Harbour through the winter are very similar in character, both 

 positions being northward of the magnetic pole. 



A maximum west deflection occurs about 1 p.m., and a maximum 

 east deflection between 2 and 3 a.m., the needle being in its mean 

 position at 6.30 p.m. and 7 a.m. 



The range of motion at Fort Foulke in 1860-61 was 42', and at 

 Van Rensselaer Harbour in 1854 was 69'; the horizontal force at 

 Fort Foulke is less than the horizontal force at Van Rensselaer 

 Harbour. 



A maximum west deflection occurs at 1 p.m. at Godhavn (as 



