Page:Narrative of the Discoveries on the North Coast of America.djvu/298

268 by Ritch's journal, that the ice on Great Bear Lake was still perfectly solid, and continued unbroken till the beginning of August; which may be considered the average term of its disruption, being a full month later than Great Slave Lake, between which and Athabasca there is a like difference.

On the evening of the 16th, having observed some signs of an opening in the ice to the east-ward, we removed to an island lying outside the mouth of the river. Here I had a fine observation at midnight of the sun's upper limb, elevated just four minutes above the visible horizon; the height of the eye being eight feet, the temperature 38° imd the barometer assumed at 30 inches. The resulting latitude, using Lynn's admirable tables, is 67° 52′ 59″; the true position was 67° 49′ 54″. On this occasion, therefore, the actual horizontal refraction exceeded the tabular by 3′ 5″; indeed, during the succeeding morning, there was much mirage, indicating a highly refractive state of the atmosphere. The