1919] REMARKS ON MAJOR G. I. TAYLOR'S PAPERS 603 the thickness of the board. The suspension both of the end piece and of the board in a vertical plane would be by four wires reducing the original six degrees of freedom to two. (Compare Theory of Sound, § 62 ; Phil. Mag. Vol. XL p. 127 (1906), Soi. Papers, Vol. v. p. 283.) Of the remaining two, one relates to the motion parallel to the wind, which is the subject of observation, and the other (rotation about the upper edge of the board) would be controlled by gravity. When the board is long, there is less objection to the rigid attachment of the end pieces to it. This method would doubtless require care in execution arid would involve the measurement of very small displacements along the wind, but for this optical resources should be adequate. It might also be applied to various parts of the length of the board, so as to separate the frictions there incurred.cised upon the board, and in the second paper corrects, as far as possible, some deficiencies in the first. These calculations are a little difficult to follow as approximations are introduced whose validity is difficult to estimate, at any rate, without the instinct which familiarity with the subject matter may bring with it. For example, at some points, the problem is treated as if it were two-dimensional, which the actual dimensions of the board do not seem to justify.