Note 147 — Chapter III · THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE.
Reading edition
Mr. R. Mallet remarks (‘Quarterly Journal of Geolog. Soc.’ vol. xxxiii., 1877, p. 745) that “the extent to which the ground beneath the foundations of ponderous architectural structures, such as cathedral towers, has been known to become compressed, is as remarkable as it is instructive and curious. The amount of depression in some cases may be measured by feet.” He instances the Tower of Pisa, but adds that it was founded on “dense clay.”