cut the ftrata in their inclination, which
is generally from north eaft to fouth weft.
Oblique flips pais acrofs the Hope. Dired
flips cut the ftrata right acrofs. All thefe
flips would be called by naturalifts, perpendicular
fifliires, and by miners, rake vein3.
A hitch is a fmall flip only affeding part of
the coal; his other remarks on this fubjed,
muft be interefting to coal proprietors.
The next interruption is that properly
called the dyke, conftfting' of hard ftone,
commonly called whinftone, of fofter ftone,
clay, gravel, or fand ; the name feems to
arife from its refemblance to a wall in the
north, called a dyke. The fofter and loofei*
forts produce much water, which renders
them difficult to be penetrated. The gajh
or gall, is very frequent, being a crack or
chafm in the coal, and its concomitant ftrata j-
and when wide, it is fometimes full of
loofe matter, fo as to partake of the nature
of-the dyke.
The {hake affeds the coal and ftrata, fo
as to break them and throw them into con-
fufion, and when large, the beft expedient
is to fink a fhaft upon the other fide.
Mr. Williams then proceeds to give fome
account of the coal ftrata to the eaft of
Edinburgh; particularly thofe neartheTem-
ple Mill, which p'refent four feams of coal.
The author then gives fome account of Arthur’s
Seat, and Salilbury Craigs, &c. and
of the great regularity of ftrata on the coaft
of Caithnefs. The author thinks, that moft
caverns, have been mineral veins.
Among'the regular ftrata, Mr. W. clafles
coal i argillite and mountain rock among
the irregular mountain limeftone, which Mr.
Kirwan fuppofes to be primitive limeftone.
Among fubftances feldom ftratiiied, he men-
n -2 tions
mam