uranium or plutonium to thermo-nuclear bombs of the " megaton" range.
	These latter have an energy release equal to one million tons or more of T.N.T. Yesterdays explosion was certainly part of the programme of thermonuclear weapon development initiated in December, 1954.
	It could have been a trigger de-vice of relatively small power. But the fact that it was released at great height suggests that it was a fairly large device. High altitude detonation ensures a minimum of local radioactive fall-out.
	Weather conditions in the Christmas Island area were almost perfect for the test, the United States weather bureau in Honolulu reported. Winds were light and would carry any fall-out away from populated areas.