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granting t o the selected boy a substantial sum of money, since the boy pays but $300 a year for what i t costs the college $800 to give him. What we ask of a boy coming t o college is, first of all, character and, second, power. Harvard, beginning 1926, sets a limitation of 1000 upon the number admitted to the freshman class. Limitation means selection. We are looking for the all-around boy. S. W. H. Classifying the Stars. A NN I E J. CANNON. Harvard Alumni Bull., 28, 565-8 (Feb. 11, 1926).-An inspiring radio talk by a famous woman astronomer, Dr. Annie J. Cannon of Harvard Observatory. The following few sentences of this four-page article may interest chemists: "Classifying the stars has helped materially in all studying of the structure of the universe. No greater problem is presented t o the human mind. Teaching man his relatively small sphere in creation, i t also encourages him by its lessons of the unity of Nature and shows him that his power of comprehension allies him with the great intelligence over-reaching all." S. W. H. Habits of Study. EDITORIAL. H a r ~ w dAlumni Bull., 28,529-30 (Feb. 4, 19261.As t o the methods of study, the records show that students are largely innocent of the knowledge of the different requirements of different tasks. They seldom think out cases, problems, exceptions, contrary positions, applications, or corollaries. Instruction in study is needed and specific directions far particular pieces of work. There is great and unnecessary waste of time in college work. Much of i t could be prevented by more careful attention on the part of instructors to the problems of teaching as such-not merely t o modes of presentation in class, but t o the guidance of indiuidualr in their learning. S. W. H.
Light Shining on Mineral Produces Electric Current. A piece of the mineral, molybdenite, one of the chief sources of the metal molybdenum, used in steel manufacture, may replace the fragile photoelectric cell in some forms of scientific work, Dr. W. W. Coblentz, of the U. 3. Bureau of Standards, told the American Astronomical Society, in session a t Philadelphia recently. Dr. Coblentz has been studying the actino-electric effect of molybdenite, the property that causes i t t o convert light energy falling on it into electrical energy. Previously he found that pieces of the mineral have closely adjacent spats which generate either positive or negative electricity. The result is that when the whole crystal is exposed to light the positive and negative currents neutralize each other, and very little effect is noted, but if a single one of the spots is selected and illuminated, a current is produced of sufficient intensity t o be indicated with a galvanometer. Very recently, however, Dr. Coblentz told the society, he has found crystals in which all of the sensitive spots give the same kind of electricity, either positive or negative. When one of these crystals is completely illuminated, a considerable current, as compared with the others, is produced. By using vacuum tube amplifiers, such as are used in radio, the current may be magnified greatly and the crystal made available as a delicate detector of light. Such a crystal is sensitive t o the visible light waves and t o the infra-red, or heat waves, which are similar, but vibrating too slowly to he visible.-Science Service Finds Economical Method for Getting Turpentine. The producers of yellow pine lumber in the South need no longer regard the producers of turpentine and rosin as enemies destroying the best part of their trees. A new method of extracting the valuable oleoresin "gum" which is the basis of naval stores conserves nearly twothirds of the wood hitherto wasted through damage caused by the long scars made on the pines near their bases. This was described by Dr. Eloise Gerry of the U.S. Forest Products Laboratory a t Madison, Wis., speaking before the American Botanical Society. Dr. Gerry, who has just returned from a tour of conferences with the naval stores producers in Mississippi, Georgia, and Florida, stated that the new method obtained a better yield of gum from a nine-inch scar than the old was able t o realize from a scar 23 inches long.-Science Senice
