In addition to this memorial volume, the Cambridge University Press, which is represented in America by The Macmillan Company, is at present publishing the collected papers of three eminent students of mathematical physics. The first volume of Lord Rayleigh’s ‘Scientific Papers’ contains seventy-eight contributions published from 1869 to 1881. The early papers show the influence of Maxwell, Lord Rayleigh’s predecessor in the chair of experimental physics at Cambridge, but it was apparently not until 1881 that he fully appreciated the importance of Maxwell’s electro-magnetic theory of light. The papers on acoustics were followed by the publication in 1877 of the classical work on the ‘Theory of Sound.’ Lord Rayleigh, at an early period, treated various optical subjects, including some of the phenomena of color vision. His explanation of the blue color of the sky and his treatment of the resolving power of telescopes are well known. The contributions on optics and acoustics have been continued to the present time, but they by no means limit his interests. There are important papers on hydrodynamics and mathematics, and longer and shorter contributions on a great range of subjects in mathematical physics, the science which at the present day is perhaps of supreme importance. The second volume of Professor Tait’s ‘Scientific Papers’ contains those published since 1881. The first volume consisted of sixty papers, and this volume, which has followed with but little delay, adds seventy-three. As must be the case in collected papers, some are elaborate treatises while others fill only part of a single page; some are extremely technical while others were first published in the ‘Encyclopædia Britannica’ and the ‘Contemporary Review.’ Among the more elaborate papers are those on the physical properties of water contributed to ‘The Voyage of H. M. S. Challenger,’ on the kinetic theory of gases, on impact and on quaternions. The third series just published by the Cambridge Press is the ‘Papers on Mechanical and Physical Subjects’, by Prof. Osborne Reynolds, of Owens College. The first volume contains forty papers from transactions and journals issued from 1869 to 1882. The most elaborate memoir is that on certain dimensional properties of matter in the gaseous state, which includes experiments on thermal transpiration of gases through porous plates and a theoretical extension of the dynamic theory of gas. Many of the papers, such as those on meteorological phenomena and the steering of vessels, are of popular interest. The Cambridge University Press is performing a work of the utmost value to science in undertaking the publication of these great volumes, and we can only regret that, in spite of the beginnings made at Johns Hopkins, Chicago, Pennsylvania and Columbia, American men of science have no such opportunities for the publication of their works as those afforded at Cambridge and Oxford. _BOTANY._