sharp points, formed of broken fossil shells, projected from them.  It was evident that the corners of the original fragments of chalk had been wholly dissolved, from presenting a large surface to the carbonic acid dissolved in the rain-water and to that generated in soil containing vegetable matter, as well as the humus-acids.  The projecting corners would also, relatively to the other parts, have been embraced by a larger number of living rootlets; and these have the power of even attacking marble, as Sachs has shown.  Thus, in the course of twenty-nine years, buried angular fragments of chalk had been converted into well-rounded nodules.

Another part of this same field was mossy, and as it was thought that sifted coal-cinders would improve the pasture, a thick layer was spread over this part either in 1842 or 1843, and another layer some years afterwards.  In 1871 a trench was here dug, and many cinders lay in a line at a depth of 7 inches beneath the surface, with another line at a depth of 51/2 inches parallel to the one beneath.  In another part of this field, which had formerly existed as a separate one, and which it was believed had been pasture-land for more than a century, trenches were dug to see how thick the vegetable mould was.  By chance the first trench was made at a spot where at some former period, certainly more than forty years before, a large hole had been filled up with coarse, red clay, flints, fragments of chalk, and gravel; and here the fine vegetable mould was only from 4 1/8 to 4 3/8 inches in thickness.  In another and undisturbed place, the mould varied much in thickness, namely, from 61/2 to 81/2 inches; beneath which a few small fragments of brick were found in one place.  From these several cases, it would appear, that during the last 29 years mould has been heaped on the surface at an average annual rate of from .2 to .22 of an inch.  But in this district when a ploughed field is first laid down in grass, the mould accumulates at a much slower rate.  The rate, also, must become very much slower after a bed of mould, several inches in thickness, has been formed; for the worms then live chiefly near the surface, and burrow down to a greater depth so as to bring up fresh earth from below, only during the winter, when the weather is very cold (at which time worms were found in this field at a depth of 26 inches), and during summer, when the weather is very dry.

A field which adjoins the one just described, slopes in one part rather steeply (viz., at from 10 deg. to 15 deg.); this part was last ploughed in 1841, was then harrowed and left to become pasture-land.  For several years it was clothed with an extremely scant vegetation, and was so thickly covered with small and large flints (some of them half as large as a child’s head) that the field was always called by my sons “the stony field.”  When they ran down the slope the stones clattered together.  I remember doubting whether I should live to see these larger flints covered with vegetable