Page:Africa by Élisée Reclus, Volume 1.djvu/461

 wood, precious drugs, and other wares brought down from Nubia and the Upper Nile. The neighbouring date groves also supply abundant cargoes for the boats proceeding to Cairo and the delta.

Under its Arabic form of As-Suân, the old Egyptian name of Suân has survived for nearly five thousand years, and under its Greek form of Syene had already become famous in classical times. To geologists it recalls the granite and "syenite" quarries, which have been excavated to the south of the city for a space of nearly

four miles. Here is still to be seen an obelisk 120 feet long, not yet entirely detached from the rock. Astronomers also are reminded by this name of the experiments here carried out by Eratosthenes, over twenty-one centuries ago. Assuming that Syene stood exactly on the line of the tropic of Cancer, which, however, is not strictly correct, and finding that at Alexandria the shadow of the gnomon stood at a fiftieth on the day of the summer solstice, from these data Eratosthenes deduced the degree of the earth's curvature, and consequently #0 far