Answer.—The mariner determines his latitude by observing the meridian altitude of a celestial star whose declination or distance from the equator is known. In the northern hemisphere for an approximate answer the pole star is generally taken, the altitude of which is nearly the latitude of the place. If an observer were standing upon the equator and looking to the north he would see the pole star on the horizon, with no altitude. If he should move three degrees north the pole star would have an altitude corresponding. At Chicago it is above the horizon about 41 degrees 50 minutes, corresponding to the latitude of this city. Owing to the apparent revolution of the pole star about a central axis, which is the true pole of the heavens, the accurate latitude can only be obtained by observing its least and greatest altitude and taking one-half their sum. The longitude of any place computed from Greenwich, Washington, or other prime meridian, is easily determined by observing the Greenwich or Washington time when the sun passes the zenith meridian. In other words, knowing the difference in time between Greenwich and the place of observation, the longitude of the place may be readily computed. A difference of time amounting to one hour represents 15 degrees of longitude east or west, as the case may be. The difference in time between Chicago and Washington is forty-three minutes, which makes the longitude of Chicago 10 degrees 45 minutes, reckoning from the legal prime meridian of the United States, which is that of Washington. Every ship carries a marine chronometer, which is a time-keeper of the most careful construction, whose accuracy has been tested with the utmost precision—which is plainly a matter of the utmost importance to a vessel when it is remembered that an error of four seconds of time represents about one and one-tenth statute miles, enough to wreck a ship on a lee shore when the captain, following the chronometer, supposed himself at a safe distance from the shoal or shore.
YEARS FOR PRESIDENTIAL ELECTION.
Streator, Ill.
Is there any easy rule for finding the years on which Presidential elections have been held or are to be held?
A. C.
Answer.—Every year divisible by four, without exception, is the year for the election of President and Vice President of the United States.
U. S. BONDED DEBT—WHEN PAYABLE.
Barton, Wis.