Sound‐speed measurements and corresponding oceanographic data were obtained aboard the bathyscaph TRIESTE to a depth of 5760 m. Subsequent measurements were made in shallow northern waters by lowering the velocimeters and Nansen bottles from a surface ship. Near‐surface measurements agree with the laboratory data of either Del Grosso or Wilson. One set of the deeper measurements aboard the bathyscaph indicates a general agreement with Wilson, but the measured values were less than values computed by Wilson's equations and this difference increased with depth. The acceleration of gravity was measured at a depth of 2286 m and the increase with depth was in rough agreement with the equation in H. V. Sverdrup'sThe Oceans(Prentice‐Hall, Inc., Englewood Cliffs, New Jersey, 1949).