Page:Popular Science Monthly Volume 70.djvu/195

Rh the desert, and their absence from the southern part. The motion is always to the north but varies somewhat with the season and the strength of the wind. Tables and curves are given in the discussion, showing the relations between the rate of motion and the wind. Only the comparatively strong winds are able to move the sand. During the year 1900 the wind was recorded stronger than ten miles per hour 1,477 times, of which the wind was southerly 1,414 times, and in all other directions only 63 times. The strongest winds are always southerly, reaching at times 20 miles per hour. Northerly winds are not strong and persistent enough to break up the symmetrical form of the dunes. The following brief table gives the mean monthly motion of the dunes:

The crescent shape is well preserved as the dune advances, except where the force or direction of the wind is affected by some adjacent object. The sand dunes are formed in different parts of the desert, and move across it till they reach the hills on the northern border. These low hills are the burial places of the dunes. As individuals they go to pieces as soon as they touch these irregular formations, and become merely confused heaps of sand. Assuming the average journey, which they travel, to be twenty-five miles, since the mean yearly motion is about sixty-one feet, the life of a sand-dune may be estimated at more than 2,000 years. Since the desert is somewhat broken in places by ravines-and low hills, it is probable that but few of them make the full journey without at some time losing their identity.

national scientific societies which met in New York City during convocation week elected presiding officers as follows: The American Society of Naturalists, Professor J. Playfair McMurrich, University of Michigan; The Astronomical and Astrophysical Society of America, Professor E. 0. Pickering, Harvard College Observatory; The American Mathematical Society, Professor H. S. White, Vassar College; The American Physical Society, Professor E. L. Nichols, Cornell University; The American Chemical Society, Professor T. Marston Bogert, Columbia University; The Association of American Geographers, Professor Angelo Heilprin, Yale University; The American Physiological Society, Professor W. H. Howell, The Johns Hopkins University; The Society of Vertebrate Paleontologists, Professor Bashford Dean, Columbia University, The American Entomological Society, Professor J. H. Comstock, Cornell University; The American Botanical Society, Professor George F. Atkinson, Cornell University; The American Psychological Association, Dr. Henry Rutgers Marshall. New York City; The American Philosophical Association, Professor H. N. Gardiner, Smith College; The American Anthropological Society, Professor Franz Boas, Columbia University.

Dr. Henry S. Pritchett and the Hon. William H. Taft have been elected trustees of the Carnegie Institution.

Brazilian government proposes to establish a national geological survey under the direction of Dr. O. A. Derby, who was for many years geologist of the state of S. Paulo. Dr. Derby went to Brazil in 1875, as a