“Professor, will you explain how you take the observation?” asked Andy.
“To be sure, certainly,” was the reply of the scientist. “It is very easy when one knows how. Here is the sextant, shaped, as you can see, like a piece of pie. The curved side has a scale on it, which is just one-sixth of a circle, hence the name of the instrument. Here is a telescope which is adjustable, and here are two glasses, one for the rays of the sun, or a star, and one for the horizon. At sea, I would use the natural horizon, but that is impossible here amongst the ice and snow, and so I use an artificial horizon made of a pan of mercury.
“When I want to take an observation, I watch my chronometer and wait until it is exactly twelve o’clock. Then I point the sextant in such a fashion that the rays of the sun, reflected downward, seem to meet or ‘kiss’ the horizon. As soon as I have the light of the sun in a direct range with the horizon, I use this thumbscrew, which sets the scale below, which, as you see, is divided into degrees, minutes, and seconds. As soon as I have read the scale by means of this magnifying glass, I consult this book I carry, the Ephemeris, or Nautical Almanac, and knowing the altitude of the sun, I readily calculate just where we are located, in degrees, minutes, and seconds north latitude.”
“It’s certainly a great instrument,” said Andy. “I’d like to try it some day.”
“You shall do so,” answered Professor Jeffer, and the very next day he allowed Andy to aid him in getting a true sight, and showed the boy how to work out the necessary calculations, and also make some allowances,—for such observations are not absolutely perfect in themselves.
They had now to advance with more caution than ever, and several days later came to some open water that looked as if it would bar all further progress. The lead was six or seven hundred feet wide, and ran east and west as far as eye could reach.
“Looks as if we were stumped,” murmured Chet. “How are we ever going to get across?”
A consultation was held, and then Barwell Dawson sent one party of Esquimaux to the eastward, and another to the westward, to look for a crossing place.
The Esquimaux were gone for two days, and during that time a fierce snowstorm came up, blotting out the landscape on all sides. It was so cold that the boys could do nothing outside, and were glad enough to crouch in an igloo for warmth. During the snowstorm, more of the dogs became sick, and four of the finest of the animals died.
“Something is wrong with them,” said Barwell Dawson, and had Dr. Slade make an examination. It was then learned that the dogs had been poisoned by eating tainted seal meat. The meat was inspected, and over a hundred pounds thrown away.