me. The peculiar chemistry through which these
changes are effected might be found, carefully studied, to throw much
light on similar phenomena in the older formations. There are quarries
in the New Red Sandstone in which almost every mass of stone presents a
different shade of color from that of its neighboring mass, and quarries
in the Old Red the strata of which we find streaked and spotted like
pieces of calico. And their variegated aspect seems to have been
communicated, in every instance, not during deposition, nor after they
had been hardened into stone but when, like the boulder-clay, they
existed in an intermediate state. Be it remarked, too, that the red clay
here,--evidently derived from the abrasion of the red rocks beneath,--is
in dye and composition almost identical with the substance on which, as
an unconsolidated sandstone, the bleaching influences, whatever their
character, had operated in the Palaeozoic period, so many long ages
before;--it is a repetition of the ancient experiment in the Old Red,
that we now see going on in the boulder-clay. It is further worthy of
notice, that the bleached lines of the clay exhibit, viewed
horizontally, when the overlying vegetable mould has been removed, and
the whitened surface in immediate contact with it paired off, a
polygonal arrangement, like that assumed by the cracks in the bottom of
clayey pools dried up in summer by the heat of the sun. Can these
possibly indicate the ancient rents and fissures of the boulder-clay,
formed, immediately after the upheaval of the land, in the first process
of drying, and remaining afterwards open enough to receive what the
uncracked portions of the surface excluded,--the acidulated bleaching
fluid?

The kind of ferruginous pavement of the boulder-clay known to the
agriculturist as _pan_, which may be found extending in some cases its
iron cover over whole districts,--sealing them down to barrenness, as
the iron and brass sealed down the stump of Nebuchadnezzar's tree,--is,
like the white strips and blotches of the deposit, worthy the careful
notice of the geologist. It serves to throw some light on the origin of
those continuous bands of clayey or arenaceous ironstone, which in the
older formations in which vegetable matter abounds, whether Oolitic or
Carboniferous, are of such common occurrence. The _pan_ is a stony
stratum, scarcely less indurated in some localities than sandstone of
the average hardness, that rests like a