IN a previous paper I have discussed the post-Tertiary Clays of Eastern England. In that paper I endeavoured to show that these clays, varying as they do in texture, composition, and contents, mark a varying geographical distribution and substratum rather than a succession of changes in time; that, so far as we can tell, they are for the most part on the same horizon, and interlock with each other, with occasional local overlaps; while they are united by one common element, namely, the presence of certain foreign boulders of the same general type in them all.