THIS may be taken to be the fourth edition of a work first published by the Physical Society in a somewhat different form. Those who know Dr. Everett need not be told that he has done everything that it is possible for an accurate, painstaking author to do, to bring each successive edition as near to perfection as possible. The value of the work to the physics investigator is exceedingly great, as everybody knows; but it is not so generally well known that it is an excellent class exercise book for students. There is much new matter in this edition, including determinations of viscosities, terrestrial magnetic elements, magnetic properties of iron and other substances, and heat measurements. Illustrations of the C.G.S. System of Units, with Tables of Physical Constants. By Prof. Everett (London: Macmillan and Co., 1891.)