In the interesting description of a faulted slate (Geol. Mag. Jan. 1884, p. 1) by Mr. J. J. Harris Teall, the writer appears to consider that all faults are due to up-and-down movements; while he seems to ignore the horizontal or transverse heaves, that is, movement of the strata from side to side. In the newer strata, which are not much moved from their original horizontal position, such as those of the South Staffordshire Coalfield, or of the Weald, the majority of the dislocations appear to be due to upward or downward movement; but this is not the case among the older contorted and crumpled rocks, where in general the horizontal heaves usually equal, if they do not exceed, the up-and-down faults in number. Consequently, while reverse faults are rare in nearly horizontal rocks, they are not uncommon among the contorted and crumpled strata.