S55 
^the Neighbourhood of Edinburgh. 
which are continued to d, meet the thick bed b on one face, 
but on the other it is met with by nearly perpendicular strata c. 
Veins of sandstone sometimes shoot from the upper and un- 
der sides of strata into the adjacent rocks. These veins in 
general are very small, not much exceeding half an inch in 
thickness. This is a phenomenon of the same nature with that 
observed at the junction of granite with gneiss, mica-slate, &c. 
Veins of sandstone, from a foot to two feet wide, traverse the 
strata of sandstone. In Fig. 1. Plate VIII. are representa- 
tions of veins of sandstone traversing sandstone, aa slate- 
clay; 6 5, strata of sandstone ; cc, veins of sandstone travers- 
ing sandstone ; and a horizontal mass of sandstone surround- 
ed by inclined strata of sandstone. 
The position of the strata and veins of sandstone in Fig. 1. 
Plate VIII., can only be explained on the supposition of this 
rock being a chemical deposite, and that, therefore, the whole 
of these appearances are the result of one process of crystalliza- 
tion, Coaly matter is sometimes intermixed with the sand- 
stone ; it also occasionally contains imbedded, disseminated, and 
venigenous clay iron-ore, iron pyrites, and calcareous spar, and 
sometimes those imbedded tree-like bodies, which many minera- 
logists consider as petrified or fossilised vegetables. 
2. Bituminous Shale^ Slate-Clay., and Drawing-Slate . — Of 
these three kinds of slate, the most frequent are the two 
first mentioned. The drawing-slate is not pure, and occurs 
principally in the greenstone quarry at BelPs Mills. 
3. Clay Iron-Ore . — This valuable ore of iron occurs in thin 
beds, in bituminous shale and slate-^clay, on both sides of the 
Water of Leith, from Bell’s Mills to Stockbridge, and has also 
been noticed in nearly all the quarries which have been opened on 
both the acclivities and the summit of the rising ground from Bell’s 
Mills to the base of the Calton Hill. The beds are either con- 
tinuous, or are naturally divided into globular or quadrangular 
distinct concretions ; and balls or concretions of the same iron- 
ore occur disseminated not only in the bituminous shale and 
slate-clay, but occasionally also in sandstone. This iron-ore 
does not appear isolated in the slate, as some have maintained ; 
on the contrary, there are distinct transitions from the pure 
slate-clay through all the intermediate shades to the perfect clay 
