I understood Professor Hayford to say that he did not believe that a fluid layer exists beneath the solid crust of the earth. The same conclusion may be drawn from the earth tide experiment which was conducted on the grounds of Yerkes Observatory by Professor Michelson and myself. It seems pretty certain that the earth tides are the same as they would be if the earth were a highly elastic homogeneous solid, both with respect to the phase and amplitude of the earth tides.The experiment was entirely successful from a physicist's standpoint. The interferometers gave very little trouble. One of them did not require readjustment during the entire year. Two were readjusted to change the width of the fringes, and on one interferometer it was necessary to re‐silver one of the mirrors. As a source of light we used commercial alternating Cooper‐Hewitt lamps, and they proved to be entirely satisfactory. The only serious interruptions were caused by breaks in the electric service due to storms, and occasional short shut‐downs by the electric light company which supplied the current. The experiment at Yerkes Observatory was continued for just one year. This is probably long enough to give values of the semi‐diurnal and diurnal tides, accurate to a few tenths of one percent. For tides of longer period the experiment should be continued for, say, five years, although possibly three years would be long