THE completion of the detailed magnetic survey of a country is a task requiring great skill and industry. We congratulate Prof. A. Tanakadate and his colleagues on the successful accomplishment of a heavy piece of work, which will be welcomed by all who are interested in the science of terrestrial magnetism. The work is the result of the voluntary cooperation of sixteen observers, of whom seven are professors or assistant professors of the Imperial University, Tokyo, the others also occupying responsible positions. Prof. Tanakadate modestly only claims for himself the position of a “reporter” who has collected the work of the different parties, but we imagine that we owe to him also the detailed discussion of the results which forms an essential portion of the volume before us. A Magnetic Survey of Japan reduced to the Epoch 1895.0 and the Sea Level. Carried out by order of the Earthquake Investigation Committee, reported by A. Tanakadate. Pp. xii + 347 and plates. (Published by the University, Tokyo, Japan, 1904.)