THE great attraction of low temperature physics as a field of research is that so many of the phenomena still lack any fundamental theory, so that the outcome of any new experiment is rarely a foregone conclusion. The outstanding phenomena at present requiring something deeper than ‘phenomen-ologica theories are superconductivity and the properties of liquid helium, and other as yet unsuspected phenomena may come to light when the new range of low temperatures below 1° K. is properly exploited. The interest of these problems was beginning to be more widely recognized just before the War, and with the resumption of scientific work after the War there has been a great expansion, particularly in the United States, of the facilities necessary for research at temperatures within a few degrees of the absolute zero. Low Temperature Physics By Dr. L. C. Jackson. (Methuen‘s Monographs on Physical Subjects.) Revised second edition. Pp. vii + 130. (London: Methuen and Co., Ltd., 1948.) 6s. net.