306 Dr Hibbert on the Distribution 
I sliaii now proceed to connect in order, all the circumstances 
attending this remarkable mass. 
The large portions of granite, quartz, or felspar, which 
distinguish the coarser kind of conglomerate rock, are either an- 
gular, or are so smoothly rounded, as to seem the result of at- 
trition. This is an appearance which immediately suggests a 
notion of the abrading effects of aqueous elements. But, on 
the other hand, these apparent fragments are not unfrequently 
seen to pass into the substance of the mass in which they are 
contained ; which substance consists of portions of a more com- 
minuted description. Here, whilst the graduation is perfectly 
evident, the line of circumscription in the larger fragments be- 
comes consequently indistinct. 
The rock, consisting altogether of conglomerated por- 
tions of granite, quartz, and felspar, is often observed to gra- 
duate into the sandstone, wdiere similar portions only occur as 
adventitious substances ; sufficiently numerous, however, to give 
to this rock also a conglomerated character. Such a transition 
appears to refer the formation of both rocks to one common date. 
The w^hole of tliis conglomerate rock is very superficial. 
Subjacent rocks of a difierent description are frequently de- 
tected under it, and these are various. At Quarf, for in- 
stance, they consist of a thin series of granite, mica-slate, and 
clay-slate ; and near Fladabister, of quartz, mica-slate and lime- 
stone : At the Nab near Lerwick, of clay-slate ; and at Grimis- 
ter, of granular quartz and clay-slate alternated. These strata, 
which are strictly fundamental considered en masse j are often 
vertical, but most frequently are inclined to the west at angles 
of about 70^. An exemplification of another kind of uncon- 
formable position thus presents itself to our notice, which con- 
sists in the inferior edges of the strata of the conglomerate rock 
coming in contact with the superior or upper edges of the fun- 
damental strata. The strata of the conglomerated rock may be 
illustrated in their position by taking any set of metallic lamel- 
lie, under different angular inclinations, and by superimpos- 
ing them on the surface formed by the upper edges of other 
metallic plates, which are fixed in the usual manner in a gal- 
vanic trouffh. It will then be seen how a fundamental surface 
O 
is formed by the superior edges of the strata lying below the 
