fur ascertaining the Deviation of the Magnetic Needle. 365 



noctial line E Q, because the vernier placed upon the moveable 

 curve is ten degrees higher than a on the index of the fixed 

 part of the arm. On the contrary, if the sight O were below 

 the equinoctial line E Q, the vernier would be depressed in 

 the same proportion below o on the index. The declination 

 will of course be shown, not only for noon and midnight, but 

 for any intermediate time, and therefore the quantity of in- 

 crease or decrease for any given time will also be shown. 



Method of Adjusting the Instrument to a Horizontal Position^ 

 hy means of the Declination of the Object. (See Fig. 5, PI. II.) 



When the instrument is set in its position by means of the 

 sun or a star, either of these objects itself will indicate when 

 the instrument is truly horizontal : for this purpose the arm 

 being previously set to the angle of the declination of the 

 sun or star, and also to the apparent time, if the sight O is 

 then found to be in a line between the object S and the other 

 sight at P, it will be evident the bottom of the instrument or 

 socket M will be parallel to the plane of the horizon. 



Appendix. — No. II. 

 Extract from Capt. Parrfs Voyage of Discovery in the Year 



1823." 



" The information obtained by Captain Lyon, on his late 

 journey with the Esquimaux, sei'ved very strongly to confirm 

 all that had before been understood from these people respect- 

 ing the existence of the desired passage to the westward, in 

 this jieighbourhood, though the impossibility of Captain Lyon's 

 proceeding further in that direction, combined with our im- 

 perfect knowledge of the language, still left us in some doubt 

 as to the exact position of the strait in question : it was certain, 

 however, tliat it lay somewhere in that directioji to which we 

 had been already so long and so anxiously looking, and that 

 its eastern entrance was still occupied by many miles of fixed 

 and therefore impenetrable ice ; but the very impediment that 

 had arrested Captain Lyon's progress, as well as our daily ob- 

 servations on the state of the ice near its outer margin, ap- 

 peared to offer a considerable hope that this, obstacle nuist in 

 the course of nature veiy soon disappear, even by the gradual 

 process of dissolution, if it were not more speedily removed 

 by one grand and total disrui)tion. 



" W^hile, therefore, Captain Lyon was accjuainting me with 

 his late |)roceedings, we shaped a course for Igloolik, in order 

 to continue our look-out upon the ice, and made (he tents very 

 accurately by the compass, after a run of five Icigues, when the 

 I lecla haiikd in shore to pick ii|) one of her nieii that liad been 



left 



