360 Lelter to the Countess of Gosford, 8c. 
little distinet systems* or basins, (as Mr. Cuvier calls them) 
forming adiversified patchwork, or piece of Mosaic, where every 
separate component stone is most accurately defined, distinct, 
and different from the piece in contact with it, the lines of de- 
marcation clean and delicate. 
“* Such is the description of a Mosaic slab}; and such will be 
found the character of our surface, when carefully examined by 
an unprejudiced eye, looking for the actual state of things, and 
not for arguments to support favoutte theories. 
“‘ These distinct little systems pass into each other, as much 
per saltum, as the component stones of the Mosaic; not a trace 
of gradation on their approach, nor any rule by which it can be 
conjectured, what will be the material of the next system it is to 
come in contact with: hy material I mean, the variety of slone, 
our only solid substance, the Ossaiura of the world, as it has 
been called by naturalists. ; 
<* When we examine this aggregate of systems forming the 
superficial part of thé world; we shall find the contiguous ones, 
though strongly discriminated from each other, yet often carrying 
with them some common properties: of Antrim and Derry the 
material, when not white limestone, is always basalt—the ineli= 
nation of the strata generally the same, (a slight ascent to the 
exterior of the area,) but the arrangement and order of the 
strata, differ in each of the systems. ” 
** As for instance, in the great facade of Cave-Hillf{ there is a 
* “TJ must state the sense in which I use the word sysfem. J mean a 
Well defined area, in which the materials and their arrangement are uni- 
form through its whole extent.” 
+ Dr. R. must bot here be understood, by the term ‘ Mosaic slab,” to be 
speaking figuratively, of a slice off the surface of the Eurth which Moses 
first described, but literaliy, of a work of art, a tessellated pavement. On 
some future occasion of more leisure, { will take an opportunity. of stating 
iny reasons of dissent from Dr. R’s position, that new “ systems” often 
(without intervening Fau/ts) succeed each other without “any rale, by 
which it can be conjectured, what will be the material of the next system 
it is to come in contact with:” and in the mean time request the Doctor 
to revise bis notes or observations, and consider attentively, what is the 
form and nature, of the bottoms of the several “systems” of which he speaks: 
of which local tracts, I conjecture, that he has yet duly considered only 
the tops or surfaces, and occasionally, parts of their end sections in cliffs 
or precipices *:—surely, on completely crossing a‘ Basin,” of Cuvier or 
other writers, we expect to see /he sume stratum or Rock emerve or rise 
again at the end of our journey, as we bad seen dip and disappear on en- 
tering on such basin?: in other words, are not ‘ Mineral Basins” mostly, 
if not all, formed in hollows or depressed parts of some individual Rock 
or stratum?; in “ Trouglis” rather, 1 should say, because I never yet saw @ 
‘round one, or near to it— J, F. 
' { Cave-Hill tagade, is situated across the Valley from Carmoney, on the 
WN of Belfast, see Phil, Mag. xxxix. p. 270,—J. F, 
Junction 
