PROF. C. COLERIDGE FARH, of Canterbury College, Christehureh, New Zealand, has sent a communication in which he advocates the preparation of accurate charts showing the lines of magnetic force running from the south magnetic pole to the north magnetic pole. Prof. Farr points out that the secular change in declination at any observing station is the parallactic angle subtended by the movement of either pole as viewed along a line of magnetic force, and he considers that the comparison of charts, showing the lines of force at different epochs, would lead to a better understanding of the nature of secular variation. The lines of force could be sketched in on existing declination charts, but there would be obvious difficulties in drawing the lines all the way from pole to pole. In forwarding Prof. Farr's letter, H. F. Skey, director of the Magnetic Observatory, Christchurch, N.Z., directs attention to the smoothed charts of such lines given by A. G. McNish in Terrestrial Magnetism, 41, 37 (1936). The question is whether unsmoothed charts on a large scale would be sufficiently reliable and sufficiently useful to justify the cost of publication.