THE OLD RED SANDSTONE. 93a 
charged; and hence the calcareous nodules in which we find 
their remains enclosed. The form of the nodule almost in- 
variably agrees with that of the ichthyolite within; it is a 
coffin in the ancient Egyptian style. Was the ichthyolite 
twisted half round in the contorted attitude of violent death ? 
the nodule has also its twist. Did it retain its natural pos- 
ture ? the nodule presents the corresponding spindle form. 
Was it broken up, and the outline destroyed? the nodule is 
flattened and shapeless. In almost every instance the form 
of the organism seems to have regulated that of the stone. 
We may trace, in many of these concretionary masses, the 
operations of three distinct principles, all of which must have 
been in activity at one and the same time. They are wrapped 
concentrically each round its organism: they split readily 
in the line of the enclosing stratum, and are marked by its 
alternating rectilinear bars of lighter and darker color; and 
they are radiated from the centre to the circumference. 
Their concentric condition shows the chemical influences of 
the decaying animal matter; their fissile character and par- 
allel layers of color indicate the general deposition which 
was taking place at the time; and their radiated structure 
testifies to that law of crystalline attraction, through which, 
by a wonderful masonry, the invisible but well-cut atoms 
build up their cubes, their rhombs, their hexagons, and their 
pyramids, and are at once the architects and the materials of 
the structure which they rear. 
Another and very different chemical effect of organic mat- 
ter may be remarked in the darker colored arenaceous de- 
posits of the formation, and occasionally in the stratified clays 
and nodules of the ichthyolite bed. In a print-work, the 
whole web is frequently thrown into the vat and dyed of one 
color; but there afterwards comes a discharging process; 
