The centre-to-limb increase in wave-length of three medium strength iron lines in the solar spectrum has been determined, using micrometer measurements of grating spectra. The observations were made at solar latitudes of approximately ±55°, and at radial distances from the centre between 85 and 100 per cent of the radius of the disk. The limb-effect curve obtained, after corrections for scattering of light, is in good agreement with the curve obtained recently at Oxford (5) for solar equatorial regions. The absolute wave-lengths in the solar spectrum of the lines used in this investigation and the vacuum arc wave-lengths of the three iron lines were determined using the method of circular channels. The centre red-shifts of the three lines, together with the limb-effect curve, give a red-shift at the extreme limb substantially exceeding the shift required by the principle of equivalence. It is shown that the line profiles of the solar lines in the grating spectra are affected by the apparatus function of the spectrograph. Allowing for this, the solar lines at the centre appeared to be symmetric but an unexplained asymmetry at the extreme limb was discovered. This indicates that wave-length measurements alone are insufficient for a determination of the nature of limb effect.