of a central and international observatory? The place might be the common property of all the civilized nations which might agree to its acquisition; for, we repeat, it must be neutral ground, a position independent of all political power, and under guarantee of all the states of the civilized world. The 180th degree would traverse Cape Prince of Wales, where it projects into Behring Strait, and this and the island of Unalashka in the Aleutian Archipelago are the only points where it would touch land. The United States, following the example of Italy, might cede to the republic of science this cape or a part of Unalashka, to be the site of an observatory in correlation with that of Levanzo.
ASSISTANT PROFESSOR OF PHYSICS IN HARVARD UNIVERSITY.
PHYSICS is a comprehensive term for the laws of the physical universe, and is gradually superseding the old term natural philosophy which held together in a disconnected manner various facts in mechanics, light, heat, sound, electricity, and magnetism. Under the head of Natural Philosophy most of us were taught that a body falling from the vertex of an inclined plane acquires the same velocity as it would if it rolled down the plane. A considerable knowledge of mathematics was required to prove this fact, and the youthful mind could hardly see the bearing of it when it was demonstrated. We were shown what we learned to call the falling machine of Atwood, which proved simple laws with such ponderousness of structure and complexity of appliances that even the name of the machine made more impression upon the memory than the laws of which it was the servant. The brightest boys could prove that the square of the velocity of a falling body was equal to twice the acceleration of gravity multiplied by the height through which it had fallen, and the rest of us mutely followed the rule, and substituted in a formula which was forgotten as soon as the exigencies of school life were over. We also carried away vague recollections of a pump which worked by means of a curiously constructed valve. We had forgotten whether the center of gravity is where the center of pressure is applied, or where specific gravity exerts itself. We remembered a tuning-fork, an electrical machine, and a big electro-magnet which lifted the smallest boy in school, and that was all that we remembered of natural philosophy. At that very age most of us, if not all, were curious about air and water, the motions of the earth and the moon, the light of the stars,