National Geographic : 1900 Feb
PRACTICAL EXERCISES IN GEOGRAPHY Longitude.-Difference of longitude (introduced under any name that is suggested by the pupils when talking freely of the relative positions of places on a rotating globe-the technical name to come in later) can be determined between two schools in any one of the three historical methods. As Strabo employed an eclipse of the moon to determine the relative easting or westing of certain points bordering the Mediterranean, so school children in different parts of the country may employ a lunar eclipse today to determine the rela tive positions of the meridians on which their homes are situated, previously determining their local solar time, and subsequently com paring the recorded time of any phase of the eclipse by correspondence As governmental parties a hundred years ago made chronometer ex peditions between neighboring national capitals, so school children may today send a watch from one school to another by express, and thus make a very good determination of difference of longitude. As modern observers employ the telegraph for time comparisons, even if separated by the whole breadth of a continent or of an ocean, so school children may today delegate some of their number to go to a telegraph office and send "time signals " from their watch (previously set to local solar time by their own observations) to an expectant party at the other end of the line. The two parties may have to wait half an hour or so to get the line "clear," but such a trifling delay should be no obstacle to success; and even such delay may be avoided if a long-distance telephone is used; then the time signals may be counted aloud by one party and directly heard by the other. Surely it is not the lack of capacity on the part of the pupils; it is not the expense involved; it is not the difficulty or the uselessness of the work that keeps such practical experiments as these out of our schools. What is the real difficulty in the way of their introduction ? Indoor Exercises.-Practicalexercises of another kind on the earth as a globe may be performed indoors.* A meridian section of the earth as a sphere and as a spheroid may be drawn to scale in order to show how vanishingly insignificant the polar flattening really is. Geographically, its value is negligible in a high-school course, however important and interesting it is in astronomy and however valuable it is historically as a proof of the earth's rotation. The height of the highest mountains, the depth of the deepest oceans, the mean alti tude of continents, the mean depth of sea floors, and the rate of in * Several of these exercises have been suggested to me by Mr W. H. Snyder, of Worcester Academy.