458 
MR. D. SHAUPE ON THE ARRANGEMENT OF THE FOLIATION AND 
creases in inclination as we recede from the centre till it becomes vertical at the 
same distance on each side of the centre ; this arrang-ement is precisely analogous to 
that of the cleavage of slates which I first described in 1846, and have found in all 
subsequent observations to be the usual disposition of the planes of cleavage. But 
this is very rarely the position of the beds of an elevated district ; when stratified 
rocks have been raised into an arch or a dome, the steepest inclination of the beds is 
usually found near the axis or point of elevation, and the inclination diminishes as 
the distance from the disturbing force increases. The contrary will undoubtedly be 
sometimes found; yet it is very seldom that we see the distant beds dip at a higher 
angle than those nearer to the axis of disturbance. But this, which is a rare exception 
in planes of stratification, is almost the universal rule with cleavage and foliation. 
The contrast just pointed out is so general, that when an observer finds it difficult 
to distinguish between planes of cleavage and stratification, as sometimes happens 
where either or both sets of planes are obscure, he will generally be right in referring 
to bedding those planes whose inclination diminishes in receding from the axis of 
elevation, and to cleavage those which become steeper at a distance from the axis. 
And a similar empirical rule will equally assist us to distinguish foliation from 
stratification. 
The contortions of gneiss and mica slate are also far more complex than are ever 
found in the most disturbed strata, and are such as could only be produced in matter 
in a state of at least semi-fluidity ; for they are not accompanied with any fractures 
across the layers of rock, such as are found in beds which have been bent after 
their deposition. The materials of the foliated rocks seem to have been in a state 
sufficiently fluid to allow the mineral ingredients to separate freely and arrange them- 
selves according to their chemical or crystalline affinities, and while that process was 
going on to have been subjected to enormous pressure along certain axes of eleva- 
tion, which has influenced the crystallizing action in so far as to have determined 
the direction of the parallel layers of different minerals, and has also raised up those 
layers into the great arches now seen and caused the contortions of certain portions 
of them. 
Finally, not only are the arches of foliation quite different from those of elevated 
strata, but the general arrangement of those arches is such as has never yet been 
found in any beds of undoubted sedimentary origin; for it must be recollected that 
the arches represented in the section, Plate XXIII. fig. 1, run across Scotland side 
by side, exhibiting traces of a symmetry which was probably perfect before it was 
disturbed by the eruptions of granite and porphyry. 
Gneiss and Mica Schist improperly termed Metamorphic. 
The term Metamorphic Rocks has been applied to gneiss, mica schist, &c., under 
the supposition that they still maintained their original bedding, with a crystalline 
character superadded to it ; when that theory is abandoned, there will be no longer 
