position, are commonly found standing nearly or quite upright in the red
clay. This fact is so common that the workmen assured me that this was
their natural position. I roughly measured one which stood vertically,
and it was of the same length and of the same relative thickness as one
of my arms. These elongated flints must get placed in their upright
position, on the same principle that a trunk of a tree left on a glacier
assumes a position parallel to the line of motion. The flints in the
clay which form almost half its bulk, are very often broken, though not
rolled or abraded; and this may be accounted for by their mutual
pressure, whilst the whole mass is subsiding. I may add that the chalk
here appears to have been originally covered in parts by a thin bed of
fine sand with some perfectly rounded flint pebbles, probably of Tertiary
age; for such sand often partly fills up the deeper pits or cavities in
the chalk.
{131} S. W. Johnson, How Crops Feed, 1870, p. 139.
{136a} Nature, November 1877, p. 28.
{136b} Proc. Phil. Soc. of Manchester, 1877, p. 247.
{138a} Trans. of the New Zealand Institute, vol. xii., 1880, p. 152.
{138b} Mr. Lindsay Carnagie, in a letter (June 1838) to Sir C. Lyell,
remarks that Scotch farmers are afraid of putting lime on ploughed land
until just before it is laid down for pasture, from a belief that it has
some tendency to sink. He adds: Some years since, in autumn, I laid
lime on an oat-stubble and ploughed it down; thus bringing it into
immediate contact with the dead vegetable matter, and securing its
thorough mixture through the means of all the subsequent operations of
fallow. In consequence of the above prejudice, I was considered to have
committed a great fault; but the result was eminently successful, and the
practice was _partially_ followed. By means of Mr. Darwin s
observations, I think the prejudice will be removed.
{139} This conclusion, which, as we shall immediately see, is fully
justified, is of some little importance, as the so-called bench-stones,
which surveyors fix in the ground as a record of their levels, may in
time become false standards. My son Horace intends at some future period
to ascertain how far this has occurred.
139