In the search for large deposits of haematite and other feebly magnetic minerals, it is suggested that mapping the magnetic residuals may be of greater value than mere linear traverses. Not only is the method more suitable for exploring virgin areas, but it also affords a means of differentiating between the effects of large deeply buried masses and small objects at shallow depths. At the same time, the graphical expression of the results on the map becomes more easily intelligible.

The application of the method to known haematite ore-bodies in South Wales has yielded striking results and the extension of the survey into an unexplored area indicates the possibility of proving at least one further large haematite deposit.