TERRESTKIAL MAGNETISM, 701 



Latitude of place of observation, 71° 2V N., long. 156° 15' W. 

 A heavy gale on December 17th stopped observations for five 

 days, raised the water 3 feet round the wall of the observatory, 

 and on December 21st the water had come within 6 inches of the 

 top of the pedestal. 



There were two series of hourly observations of declination 

 from November 1852 to June 1853, and from October 1853 to 

 June 1854. The influence of the disturbances at Point Barrow 

 was to occasion a small mean deflection of the needle towards the 

 east, thus slightly increasing the easterly declination. 

 . The mean declination at Point Barrow is 41° E. 



There are two epochs of maximum disturbance, the principal at 

 from 7 to 9 a.m., when the proportion reaches twice the average 

 amount, and a lesser maximum at from 11 p.m. to 1 a.m. The 

 principal minimum is from 3 to 6 p.m., and a smaller minimum at 

 3 or 4 a.m. 



The amount of disturbance at the different hours as compared 

 with Toronto shows that it is regulated by a law which has refer- 

 ence to the hours of solar time ; but the easterly disturbances 

 at Point Barrow correspond to the westerly disturbances at 

 Toronto. 



The principal maximum disturbance at 7 to 9 a.m. is occasioned 

 chiefly by easterly disturbances, and the lesser maximum by westerly 

 disturbances; the minimum for both easterly and westerly dis- 

 turbances being from 3 to 6 p.m. The easterly are in all respects 

 as to time and range more strongly marked than the westerly dis- 

 turbances, but each probably consists of a single progression in the 

 24 hours, and the double maxima and minima would seem to be 

 capable of being resolved into two single progressions (easterly and 

 westerly), having different hours of maximum and minimum. 



For the further elucidation of these relations of disturbances 

 and deflections at different stations, observations should include 

 variations of the magnetic force as well as of the magnetic 

 direction. 



The- mean dip in each year was found to be 81° 36', being 

 greatest in February, March, and April in 1852-53, and in 

 February, March, and June in 1853-54, and least in November 

 and December 1852-53, also in December and January 1853-54; 

 the range throughout the year being about 10'. 



Both at Toronto and Point Barrow the north end of the magnet 

 is at its easterly extreme at 8 a.m. ; in returning towards the 

 west its motion is more rapid than at any other part of the 

 24 hours; that it passes its mean position at 11 a.m., and reaches 

 its westerly extreme at 1 p.m. The subsequent motion to the 

 east is slower at Point Barrow than at Toronto, and at both 

 stations is checked by a small retrogression towards the west, 

 which would seem to be due to the disturbances. (Phil. Trans., 

 1857, p. 508.) 



