VOL. II. of “Contributions from the Jefferson Physical Laboratory of Harvard” consists of reprints of eighteen papers which have appeared in the Physical Review and elsewhere during the years 1913–14. The research work which these papers represents was largely aided by the Coolidge and other funds for original research. Dr. Bridgman's high-pressure work occupies a large share of the volume. We have already noticed in these columns his paper on the technique of high-pressure experimenting. From his other papers in the present volume it seems now clear that the melting points of solids continue to rise as the pressure is increased to 12,000 kilos, per sq. cm. at a rate which shows no sign of the existence of maximum melting points or of any critical points in the melting-point curves. Of the late Prof. B. O. Peirce's work on the magnetisation of short cylinders we gave an account some time ago. Prof. H. C. Hayes shows that a rate-flow meter for fluids depending on the difference of pressure at the centre and side of a vortex can be constructed to give results correct to within 1.5 per cent. Mr. J. Coulson describes an apparatus for reproducing and measuring very short intervals of time depending on the difference of time an elastic wave takes to pass from a point near the middle of a rod to the two ends. Prof. Lyman has investigated the arc and spark spectra of mercury in the region from λ=187o to 1270, and has found that the positions of the lines do not agree with the predictions of Hughes from photo-electricity data. In the theoretical field, Prof. Hall shows that the phenomena of thermo-electricity seem to be due to free electrons, but that electric conduction seems to a large extent independent of them. Prof. Webster concludes that the phenomena of radiation, of optics, and of photo-electricity can be explained, without discarding the classical dynamics, by the aid of the Parson magneton—a ring of electrons of diameter one-tenth that: of a hydrogen atom moving round its axis with the speed of light. From these short notes it will be seen that the volume constitutes a record of research of which any university may be proud.