692 



TERRESTRIAL MAGNETISM. 



" diminished, produced irregularities that rendered observations 

 " on board ship of little or no value towards a knowledge of the 

 " true variation." 



Abstract of the times in which 100 vibrations of dipping needle 

 were performed : 



Place. 



Lat. 



Long. 

 W. 



Ill 

 Meri- 

 dian. 



First 

 Arc. 



Perpendicular -c-^-^. 



to the l*^'^^* 



Meridian. 



Arc. 



Regent's Park 

 Shetland 

 Davis Strait 

 Hare Island 

 Baffin's Bay 



Davis Strait 

 Regent's Park 



51 31 



60 09 



68 22 



70 26 



75 05 



76 45 



76 08 



70 35 



51 31 



08 



1 12 



53 50 



54 52 

 60 23 

 63 06 

 76 00 

 78 21 

 66 55 



08 



s. 



o 



49f 



74 



20 



83 



21 



83 



27i 

 23^ 



84 



84 



15 



85 



16 



85 



16 



83 



02 



70 



8 18 



90 

 90 

 90 

 90 

 90 



90 

 90 

 90 

 90 



2. Parry's First Voyage in search of a North- vtest Passage. 



Magnetic Observations at Observatory, Melville Island. — (Made 

 by Captain Sabine.) 



Variation - 127° 47' 50'^ E. 



Dip - - 88° 43' (on July 17, 18, 19, 1820). 



Dipping Needle. — To adjust the needle to the magnetic meri- 

 dian, a box containing an horizontal needle and card was fitted to 

 the instrument. The variation is the mean of a great number of 

 observations extending from October to July. 



The intensity of the magnetic force was determined by the 

 dipping needle in July 1820, by determining the time of 100 

 vibrations in and perpendicular to the magnetic meridian, 

 observing the amount of swing after every ten vibrations, and 

 the results were compared with determinations made in Regent's 

 Park in March 1819 and December 1820:— 



The time of 100 vibrations in Regent's Park, 8m. 2s., in the 

 meridian. 



The time of 100 vibrations in Regent's Park, 8m. 18- 5s., per- 

 pendicular to the meridian. 



The time of 100 vibrations in Melville Island, 7m. 26 •25s., in 

 the meridian. 



The time of 100 vibrations in Melville Island, 7m. 26 •4s., 

 perpendicular to meridian. 



The time of 100 vibrations in Regent's Park, 8m. 00s., in 

 magnetic meridian. 



Observations for Horizontal Intensity were also made with bars 

 of steel suspended horizontally in a stirrup by a silk line, and 

 allowed to vibrate on each side of the magnetic meridian, the 

 readings being taken at each 10 vibrations. 



