Motion. Anything that changes position. There are two kinds of motion (a) simple motion and (b) compound motion. Simple motion can be either translated or rotary, while compound motion is both translated and rotary, so that while a body is being translated, or moved through space, it is also rotating on its axis. The Sun and planets, then, have compound motions.
Nature. Everything contained in space that has not been shaped by human hands.
Nautical almanac. The American Nautical Almanac is a book of the stars published by the Bureau of Navigation of the United States. It is published three years in advance and is sold by the Superintendent of Documents, Washington, D. C., at 30 cents per copy. This is designed chiefly for the use of navigators of ships. It gives the exact positions of the Sun, Moon and planets and much other astronomical information. It is based upon the calculations made by the United States Naval Observatory; these are printed in the Nautical Almanac, and on this all other almanacs are based.
Northern lights. See Aurora Borealis.
Obscured. Hidden from sight.
Official Handbook of the Boy Scouts. A book published by the organization of Boy Scouts and which contains the rules and regulations of that organization and the requirements they must meet in order to win merit badges.
Offset. To equal; to balance.
Opposition. [See Appendix].
Optic Nerve. The nerve that carries the impression of light received by the eye to the brain.
Orbit. The path followed by a body. Atoms have orbits as well as the stars. The paths followed by planets and comets round the Sun.