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Let the line N be the length of the travel of light in air during the time in which, within the crystal, it makes, from the centre C, the spheroid QCqgM. Then having drawn CO perpendicular to the ray CR and situate in the plane through CR and AH, let there be adjusted, across the angle ACO, the straight line OK equal to N and perpendicular to CO, and let it meet the straight line AH at K. Supposing consequently that CL is perpendicular to the surface of the crystal AEHF, and that CM is the refraction of the ray which falls perpendicularly on this same surface, let there be drawn a plane through the line CM and through

**KCH**, making in the spheroid the semi-ellipse QMq, which will be given, since the angle MCL is given of value 6 degrees 40 minutes.
Captain, Sir John Franklin,

**KCH**; Commander, James Fitzjames; Lieutenants, Graham Gore, Henry T. Le Vesconte, James William Fairholm; mates, Charles T. des Vaux, Robert O'Sargent; second master, Henry F. Collins; surgeon, Stephen Stanley; assistant surgeon, Harry D.S. Goodsir; paymaster and purser, Charles H. Osmer; master, James Reid, acting; fifty-eight petty officers, seamen, etcetera.