course of the last chapter we wholly
left out of our account of mountain lines that group which was called
"Lines of Rest." One reason for doing so was that, as these lines are
produced by debris in a state of temporary repose, their beauty, or
deformity, or whatever character they may possess, is properly to be
considered as belonging to stones rather than to rocks.

Sec. 14. Whenever heaps of loose stones or sand are increased by the
continual fall of fresh fragments from above, or diminished by their
removal from below, yet not in such mass or with such momentum as
entirely to disturb those already accumulated, the materials on the
surface arrange themselves in an equable slope, producing a straight
line of profile in the bank or cone.

The heap formed by the sand falling in an hour-glass presents, in its
straight sides, the simplest result of such a condition; and any heap
of sand thrown up by the spade will show the slopes here and there,
interrupted only by knotty portions, held together by moisture, or
agglutinated by pressure,--interruptions which cannot occur to the same
extent on a large scale, unless the soil is really hardened nearly to
the nature of rock. As long as it remains incoherent, every removal of
substance at the bottom of the heap, or addition of it at the top,
occasions a sliding disturbance of the whole slope, which smooths it
into rectitude of line; and there is hardly any great mountain mass
among the Alps which does not show towards its foundation perfectly
regular descents of this nature, often two or three miles long without a
break. Several of considerable extent are seen on the left of Plate
+46+.

Sec. 15. I call these lines of rest, because, though the bulk of the mass
may be continually increasing or diminishing, the line of the profile
does not change, being fixed at a certain angle by the nature of the
earth. It is usually stated carelessly as an angle of about 45 degrees,
but it never really reaches such a slope. I measured carefully the
angles of a very large number of slopes of mountain in various parts of
the Mont Blanc district. The few examples given in the note below are
enough to exhibit the general fact that loose debris lies at various
angles up to about 30 deg. or 32 deg.; debris protected by grass or pines may
reach 35 deg., and rocky slopes 40 deg. or 41 deg., but in continuous lines of rest
I never found a steeper angle.[98]

Sec. 16. I speak of some rocky slopes as