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After that dramatic standoff, Dr. Millikan has steadily, almost imperceptibly, retreated from his position, while Dr. Compton has maintained and strengthened his. Millikan's billion-volt maximum announced at Atlantic City cracked when he recognized rays at the Equator of 10,000,000,000 volts. This in turn involved yielding a point to Sir James Jeans, who had held that cosmic rays were not "birth cries" but "death cries'' of matter annihilated in the wasting stars. Ten billion volts, honest Dr. Millikan conceded, could only come from the complete annihilation of atoms. Dr. Thomas H. Johnson of the Bartol Research Foundation and others found that more cosmic rays were slanting to the east than to the west. Theorists had already shown that a positively charged corpuscle would have an eastward slant impressed on it by the Earth's magnetic field. One important Millikan defense had been that the particles observed were terrestrial secondary rays knocked out of the air by primary cosmic photons. If this were true, the latitude variation showing corpuscles should decrease toward the thin top of the atmosphere where targets were fewer. It was found, on the contrary, that in the upper air the latitude effect increased from 20% to 97½%. Last autumn Dr. Millikan, addressing the National Academy of Sciences, presented recordings from nine ships showing that cosmic rays are stronger in the Eastern hemisphere than in the Western. This longitude effect could only have reference to charged particles, since the geomagnetic field is stronger in India than in the U. S. Photons were left out of the picture. Much of this history was traced by Dr. Compton last week. But with data from a dozen scientific satrapies covering 100 localities, including Antarctica, he was ready with specific answers to specific questions. What are cosmic rays? Since the latitude effect showing electric particles increases from about 20% at sea level to some 97% near the top of the atmosphere, it stands to reason that primary cosmic radiation 400 or 500 miles out in space must consist of at least 99% particles. The remaining 1% may be particles or photons or both. By checking theoretical absorption rates against those actually observed three prominent ingredients have been found in the cosmic ray. One consists of nearly equal parts of positive and negative electrons. Another, which does not penetrate far below the top of the atmosphere, is alpha particles, or positively charged nuclei of helium. The third, which reaches sea-level easily, is protons, or positively charged nuclei of hydrogen. How power fid are they? The most powerful rays can penetrate 3,200 ft. of water or 292 ft. of solid lead. For a vertical primary ray to reach the Equator requires 20,000,000,000 volts. Showers of particles knocked out of atomic nuclei by cosmic rays indicate occasional energies of 600 billion volts. Where do they come from? Directional measurements show no evidence that cosmic rays come from the sun, or the neighboring stars, or even from the great mass of stars in the Milky Way. Years ago Dr. Millikan therefore guessed that they came from the vast reaches beyond the Milky Way. The whole Milky Way is slowly rotating, carrying Earth along in the direction of Vega at some 200 mi. per sec. Therefore if the cosmic rays come from outside the great Milky Way wheel, whatever side of Earth happens to be facing Vega