MR. J. A. Lee by his commentary (Journal, 22, 267) rightly suggests that instead of saying in my par. 1 (Journal, 21, 504), as I did after quoting Mr. Carr and Sq. Leader Scott, R.A.F. (Journal, 20, 406, sec. 2, par. 1) my words ‘—and from this deducing velocity and position of the vehicle,’ I could better have simply continued their words, ‘From this acceleration we can then, by successive mathematical integrations, deduce first velocity and secondly the displacement of the vehicle.’ Furthermore, it was superfluous and careless of me to add my quite worthless opinion as to soundness and virtue of expression on their part, but I comfort myself, and I hope also Mr. Lee, with the knowledge that there is no evidence that my opinions have ever previously had any effect whether for good or ill. To the extent, if any, that I can understand Mr. Lee's learned commentary, I believe I quite agree with him and am especially grateful for the clear definition given in his final sentence. If, however, an answer has been given to the question I raised as to the connection of Schuler's 1923 paper with inertial navigation, I am not presently aware of this.