Deep seismic sounding of the earth’s crust was conducted along a line of seven recording sites running from Flin Flon to Mafeking, Manitoba. Two interfaces, the Conrad and the Mohorovičić discontinuities, were distinguished. The following head‐wave types were observed: P*, SPP, SPS, S*, [Formula: see text], PSPSP, SSPSS, SPPPS, SSPPS, and PSPSS. Even though only a single shotpoint was used, it was found possible to determine velocities, layer thicknesses, and structure, using the interpretational possibilities of converted head waves. Discontinuities were determined as follows: Conrad—rises from 15.5±1‐km depth near Flin Flon to something just under 10‐km depth near Mafeking; Mohorovičić—rises from 34±1‐km depth near Flin Flon to 31±1‐km depth near Mafeking. Velocities are as follows upper layer—[Formula: see text], [Formula: see text]; intermediate layer—[Formula: see text], [Formula: see text]; lower layer—[Formula: see text]. Ratio of vertical to horizontal radial displacement was experimented with as a method of identifying converted head waves, and was found to be definitive for head waves arriving from the Mohorovičić as an S wave. Traveltime was found to be effective in wave identification. Comparison of the observed gravity curve with the curve computed for the seismic model indicates that depths and densities related to the model do not totally explain the observed gravity. There is reason to believe that masses of anomalous density within the granite layer are responsible for the disagreement.