Use of Sumner Lines in Navigation

Abstract

CAPT. TIZARD'S reference to my book entitled “The Sumner Line,” etc. (NATURE, July 1, vol. cv., p. 552), contains an error which should be corrected. Hisstatement regarding what he calls the zenith point, “which spot is named by Mr. Comstock the sub-polar point,” seems to imply that I have introduced a new name not approved in the criticism that follows. In fact, I have nowhere used the obnoxious term “sub-polar point,” but have employed in this connection a well-known phrase, “the sub-solar point,” for which I can claim no authorship. See Young, “General Astronomy,” 1898 edition; Muir, “Navigation,” 1918, et al.