23 FEBRUARY 1924, Page 26

The fourth volume of Dr. Mellor's monumental treatise

begins with three chapters on the structure of matter, radium

and radio-activity, and the architecture of matter, which are a marvel of concise and accurate statement. • No more compre- • hensive account of the historical facts and the latest theories could possibly be compressed into 200 pages. We note with interest the. statement that, if lead could be transmuted into gold, the gold would be only an insignificant by-product, since the energy liberated would be worth far more. The other chapters deal exhaustively with beryllium, magnesium, zinc and cadmium, and mercury. The very full references to original papers continue to make Dr. Mellor's work invaluable —or at least worth its rather high price—to serious students of chemistry.