22 OCTOBER 1921, Page 23

The Imperial Institute is issuing through Mr. Murray a series

of " monographs on mineral resources with special reference to the British Empire." One is Silver Ores, by Mr. H. B. Cronahaw (6s. net), in which the sources of supply in the British Empire and in other countries are compactly described. Mexico is the chief source, with the United States a close second and the British Empire third. Another volume is. Petroleum, prepared jointly with the Petroleum Department -by Mr. H. B. Cronshaw (5s. net), which is a capital summary of a large and most important subject. Two-thirds of the petroleum produced in the world is contributed by the United States. The American and Mexican outputs, taken together, amounted in 1920 to 86,000,000 tons out of the world's total of 97,500,000 tons.