VISITORS to the Loan Collection of Scientific Apparatus at South Kensington in 1876 will remember a remarkable series of permanent steel magnets contributed from the museum of the Teyler Foundation of Haarlem. Most of these were the work of a famed artificer of the name of van Wetteren, who during a period of thirty years has been occupied in the construction of magnets of excellent quality, under the advice and with the co-operation successively of MM. Logeman, Elias, and van Willigen. The last named of these, whose posthumous monograph lies before us, devoted himself for the last four years of his life to important researches in magnetism. Sur le Magnetisme des Aimants Artificiels. Par V. S. M. van der Willigen. (Haarlem: Les Heritiers Loosges, 1878.)