The investigations dealt with in this memorandum were commenced in the autumn of 1895, and have been carried on, as opportunity permitted, until July of the present year. The observations were made in 1895 and 1896 by Mr. F. B. Stead, in 1897 by Mr. S. D. Scott and myself, and in 1898 by myself. A preliminary memorandum, dealing with the observations made in 1895, has already been submitted to the Committee by Mr. Stead. As a matter of general convenience it is reprinted as an appendix to this Report.