1815.} On the Red‘ Sand-stone Formation. 15 
sand-stone districts in Scotland, in beds, hills, and veins. The 
following are a few of the bocalities of this rock: Arran, East 
Lothian, Ochils, Pentlands, Angus-shire, &c. 
8. Green-stone. — Beds, imbedded. cotemporaneous. masses, 
mountain masses, hills, and veins, of this rock occur in the red 
sand-stone formation of Scotland. ~Thus it is met with in East and 
Mid Lothian, Ochil Hills, Arran, Bute, Renfrewshire, Ayrshire, 
Angus-shire, &c. 
.9., Pitch-stone—Green and black coloured varieties of this rock 
are met with in the form of imbedded masses, beds, and veins, in 
the red sand-stone of the Island of Arran. 
10. Felspar.—Beds of compact felspar, often passing into clay- 
Stone, occur in the red sand-stone of Arran, Pentland Hills, Ochil 
Hills, &c. 
_ Ll. Porphyry. — Varieties of this rock, namely, clay-stone, 
horn-stone, and felspar-porphyry, occur in beds, hills, and veins, 
in the red sand-stone formation. ‘The Pentland and Ochil Hills, 
the Island of Arran, the upper ward of Lanarkshire, Angus-shire, 
afford examples of porphyry in red sand-stone. 
_ 12. Lime-stone and Lime-stone Conglomerate. —These rocks 
occur in beds in the red .sand-stone of East and Mid Lothian, in 
that of the Ochil and Pentland Hills, of Arran, Dumfrieshire, 
Ayrshire, Lanarkshire, Renfrewshire, Angus-shire, &c. 
13. Coal.—Of this mineral several kinds occur in the red sand- 
stone, viz. glance-coal, slate-coal, and pitch-coal 3 and they are 
met with in Arran, Dumfrieshire, Lothian, &c. 
From the short enumeration just given, it is evident that the red 
sand-stone formation is much more interesting than has been gene- 
rally imagined. ‘The great variety and abundance of trap, pitch- 
stone, and porphyry rocks, contained in it, their transitions into 
each other and into the sand-stone and clay are very striking facts in 
their natural history, and deserving the particular attention of those 
who take an interest in the volcanic and neptunian theories of their 
formation. Those naturalists who are inclined to think favourably 
of the opinion which maintains the chemical formation of sand- 
stone will adduce the various kinds of structure exhibited by the 
red sand-stone as so many facts illustrative of its plausibility ; and 
the miner and engineer, if they adopt this opinion, will probably 
obtain an easy solution of many difficulties that occur in their re- 
spective arts, and practical rules of value and importance to them, 
