I intended that Marvin should take all the observations up to his farthest, and Bartlett all beyond that to his farthest.

This was partly to save my eyes, but principally to have independent observations with which to check our advance.
The mercury of the artificial horizon was thoroughly warmed in the igloo; a semi-circular wind-guard of snow blocks two tiers high was put up, opening to the south; a musk-ox skin was laid upon the snow inside this; my special instrument box was placed at the south end and firmly bedded into the snow in a level position; the artificial horizon trough, especially devised for this kind of work, was placed on top and the mercury poured into it until it was even full, when it was covered with the glass horizon roof.
[Illustration: MARVIN TAKING AN OBSERVATION IN A SNOW SHELTER] Marvin, then lying full length upon his face, with his head to the south and both elbows resting upon the snow, was able to hold the sextant steady enough to get his contact of the sun's limb in the very narrow strip of the artificial horizon which was available.

A pencil and open note-book under the right hand offered the means of noting the altitudes as they were obtained.
The result of Marvin's observations gave our position as approximately 85 deg.

48' north latitude, figuring the correction for refraction only to a temperature of minus 10 F., the lowest temperature for which we had tables.

It was from this point that, reckoning twenty-five miles for our last two marches, we calculated the position of Camp 19, where Borup turned back, as being 85 deg.