HIGH FREQUENCY RAYS—MILLIKAN 201 
(4) That these hard rays stimulate, upon striking matter, softer 
rays of about the hardness predicted by the theory of the Compton 
effect ; 
(5) That these rays come into the earth with equal intensity day 
and night and at all hours of the day or night, and with practically 
the same intensity in all directions. 
Mr. I. 8. Bowen, Dr. Russell Otis, Mr. G. Harvey Cameron and 
myself, all of whom have participated in this investigation and have 
received invaluable aid from the instrument maker, Mr. Julius Pear- 
son, will publish full details of this work elsewhere. 
