COSMIC RADIATION.

pp175-185, five figures in the text. Removed from ANNUAL REPORT OF THE BOARD OF REGENTS OF THE SMITHSONIAN INSTITUTION FOR THE YEAR ENDED JUNE 30, 1938. VG. In plastic report covers. "The study of cosmic radiation is rather a curious one. It is related ultimately to astronomy, to geophysics, and to physics. The subject started about 1900 with the discovery by C.T.R. Wilson, and by Elster and Geitel, that the air in a closed vessel had a slight residual conductivity. We know now that this residual ionization is, in fact, due to atomic particles of enormous penetrating power coming into the earth's atmosphere from some sources outside the solar system, but exactly what these particles are, or where they come from, or how they were formed, or when, we still do not know." I am not a student of astronomy, but I assume we know a bit more now than when this article was written.