In placing the trough and the roof on the top of the instrument box, the trough is placed so that its longer diameter will be directed toward the sun.
A skin is then thrown down on the snow close to the box and north of it, and the observer lies down flat on his stomach on this, with his head to the south, and head and sextant close to the artificial horizon.

He rests both elbows on the snow, holding the sextant firmly in both hands, and moving his head and the instrument until the image or part of the image of the sun is seen reflected on the surface of the mercury.
The principle on which the latitude of the observer is obtained from the altitude of the sun at noon is very simple.

It is this: that the latitude of the observer is equal to the distance of the center of the sun from the zenith, plus the declination of the sun for that day and hour.
The declination of the sun for any place at any hour may be obtained from tables prepared for that purpose, which give the declination for noon of every day on the Greenwich meridian, and the hourly change in the declination.
Such tables for the months of February, March, April, May, June, and July, together with the ordinary tables for refraction to minus 10 deg.
Fahrenheit, I had with me on pages torn from the "Nautical Almanac and Navigator." [2] Ignorance and misconception of all polar matters seem so widespread and comprehensive that it appears advisable to introduce here a few a b c paragraphs.

Anyone interested can supplement these by reading the introductory parts of any good elementary school geography or astronomy.
The North Pole (that is, the geographical pole as distinguished from the magnetic pole, and this appears to be the first and most general stumbling block of the ignorant) is simply the point where that imaginary line known as the earth's axis--that is, the line on which the earth revolves in its daily motion--intersects the earth's surface.
Some of the recent sober discussions as to the size of the North Pole, whether it was as big as a quarter, or a hat, or a township, have been intensely ludicrous.
Precisely speaking, the North Pole is simply a mathematical point, and therefore, in accordance with the mathematical definition of a point, it has neither length, breadth, nor thickness.
If the question is asked, how closely can the Pole be determined (this is the point which has muddled some of the ignorant wiseacres), the answer will be: That depends upon the character of the instruments used, the ability of the observer using them, and the number of observations taken.
If there were land at the Pole, and powerful instruments of great precision, such as are used in the world's great observatories, were mounted there on suitable foundations and used by practised observers for repeated observations extending over years, then it would be possible to determine the position of the Pole with great precision.
With ordinary field instruments, transit, theodolite, or sextant, an extended series of observations by an expert observer should permit the determination of the Pole within entirely satisfactory limits, but not with the same precision as by the first method.
A single observation at sea with sextant and the natural horizon, as usually taken by the master of a ship, is assumed under ordinary satisfactory conditions to give the observer's position within about a mile.
In regard to the difficulties of taking observations in the arctic regions, I have found a tendency on the part of experts who, however, have not had practical experience in the arctic regions themselves, to overestimate and exaggerate the difficulties and drawbacks of making these observations due to the cold.
My personal experience has been that, to an experienced observer, dressed in furs and taking observations in calm weather, in temperatures not exceeding say 40 deg.

below zero Fahrenheit, the difficulties of the work resulting from cold alone are not serious.