therefore, the fragments of burnt marl and cinders had been covered in the course of 15 years by a layer of fine vegetable mould, only 21/2 inches in thickness, excluding the turf.  Six and a half years subsequently this field was re-examined, and the fragments were now found at from 4 to 5 inches beneath the surface.  So that in this interval of 61/2 years, about 11/2 inch of mould had been added to the superficial layer.  I am surprised that a greater quantity had not been brought up during the whole 211/2 years, for in the closely underlying black, peaty soil there were many worms.  It is, however, probable that formerly, whilst the land remained poor, worms were scanty; and the mould would then have accumulated slowly.  The average annual increase of thickness for the whole period is .19 of an inch.

[Illustration:  FIG. 1. 
Section of the vegetable mould in a field, drained and reclaimed
    fifteen years previously; a, turf; b, vegetable mould without
    any stones; c, mould with fragments of burnt marl, coal cinders,
    and pebbles; d, sub-soil of black, peaty sand with quartz
    pebbles.]

Two other cases are worth recording.  In the spring of 1835 a field, which had long existed as poor pasture, and was so swampy that it trembled slightly when stamped on, was thickly covered with red sand so that the whole surface appeared at first bright red.  When holes were dug in this field after an interval of about 21/2 years, the sand formed a layer at a depth of 3/4 inch beneath the surface.  In 1842 (i.e., seven years after the sand had been laid on) fresh holes were dug, and now the red sand formed a distinct layer, 2 inches beneath the surface, or 11/2 inch beneath the turf; so that on an average .21 inches of mould had been annually brought to the surface.  Immediately beneath the layer of red sand the original sub-stratum of black, sandy peat extended.

A grass field, likewise not far from Maer Hall, had formerly been thickly covered with marl, and was then left for several years as pasture; it was afterwards ploughed.  A friend had three trenches dug in this field 28 years after the application of the marl, and a layer of the marl fragments could be traced at a depth, carefully measured, of 12 inches in some parts, and of 14 inches in other parts.  This difference in depth depended on the layer being horizontal, whilst the surface consisted of ridges and furrows from the field having been ploughed.  The tenant assured me that it had never been turned up to a greater depth than from 6 to 8 inches; and as the fragments formed an unbroken horizontal layer from 12 to 14 inches beneath the surface, these must have been buried by the worms whilst the land was in pasture before it was ploughed, for otherwise they would have been indiscriminately scattered by the plough throughout the whole thickness of the soil.  Four and a half years afterwards I had three holes dug in this field, in which potatoes