220 SIR ROBERT CHRISTISON, BART., ON FOSSIL TREES 
mineral mater crystallising in the cells, and thus defines the cell-walls sharply 
before the microscope. But in other places the crystallising force of the 
mineral matter is so great that the mixed carbonates assume their crystalline 
form on a much larger scale, pushing aside the organic textures altogether, and 
substituting masses of pure radiated crystallisation. 
Addendum. 
[ July 1, 1874.—Soon after the Society’s meetings were over for this season, 
a newspaper notice drew my attention to the discovery, in the sandstone quarry 
of Redhall, of a fossil tree of great size, which proves to be undistinguishable in 
any essential respect from the araucarious fossils of Craigleith and Granton. This 
is, On various accounts, too curious a fact not to deserve to go forth with those 
recorded in the preceding narrative ; and I therefore add here a few notes from 
a paper on the subject which was read to the Edinburgh Botanical Society. 
A new quarry, close to one which has been long worked, was lately opened 
on the property of Redhall, near Slateford, 24 miles west from Edinburgh. It 
is 4 miles from Granton, and 24 from Craigleith; and the three quarries are nearly 
in a right line, in a direction from north to a little west of south. Under the 
soil is a thick bed of gravelly sand, from 8 to 20 feet in depth, containing very 
many boulders near the bottom, some of which are of great size. In the lower 
parts of this bed the sand has begun to consolidate into sandstone. Beneath 
it there is a succession of white sandstone beds about 15 feet thick, 2°426 
in density, very like that of Craigleith, but less hard—more easily worked or 
pulverised. Lower beds succeed, of a pale yellowish hue, permanent, and 
not deepening under atmospheric exposure. Its density is 2°391. This, too, is 
brittle at first, but becomes tougher in time; and, being easily worked, is much 
in request by builders. Both the white and yellow stone have been formed by 
accretion, not by agglutination ; for acids indicate only 1°5 per cent. of foreign 
matters, which are lime, magnesia, and oxide of iron,—the lime in the form of 
sulphate. But in various places the sandstone becomes ochrey under exposure, 
and then it presents the same external characters and the same chemical com- 
position as the “bastard whin” of Craigleith. In particular, it effervesces 
strongly with diluted acids, and yields to them much lime, magnesia, and iron- 
oxide. There is a great resemblance, therefore, between the sandstone of the 
three quarries, and also the accidents which are apt to alter it. 
A considerable variety of vegetable fossils has been met with in the new 
Redhall quarry. Of those shown to me, all but one seemed to belong to ferns 
and other acrogenous plants of coarsely cellular, loose texture, and consequently 
presented the appearance of casts, with the interior filled with sandstone 
destitute of traces of organic structure. The single exception proves to be a 

