JET.—WEALDEN COAL. 73 
lignite, and the vascular tissue may be detected even in the 
most solid masses; when prepared in very thin slices, it 
appears of a rich brown colour by transmitted light, and the 
woody texture is visible to the naked eye. Jet is found in 
great purity and abundance in the cliffs of alum-shale on 
the Yorkshire coast, which were celebrated in the early 
centuries for the production of this substance. At Whitby 
and Scarborough extensive manufactories of ornaments and 
trinkets of jet are established. The sandstone cliffs near 
Whitby contain masses of a very compact variety, locally 
termed stone-jet. In the front of the cliff, on the north- 
west side of Haiburn Wyke, the stump of a tree was 
observed in an erect position, about three feet high, and 
fifteen inches in diameter; the roots traversed a bed of shale, 
and were in the state of coarse jet, but the trunk, which 
extended into the sandstone, was in part silicified, while other 
portions were decayed and had a sooty aspect.* 
Thin seams and layers, and nodular masses, as well as 
regular coal-fields of lignite, occur in the tertiary formations. 
At Castle Hill, near Newhaven, in Sussex (Wond. p. 239), 
a seam of lignite resembling the surturbrand of Iceland, a 
few inches thick, is interposed between strata of red marl 
in which are carbonized leaves of dicotyledonous trees. 
At Alum Bay in the Isle of Wight, a layer of lignite 
occurs between the beds of vertical gravel and sand of that 
interesting locality. 
WeEALDEN Coat.—The Wealden formation, in some 
districts, contains layers of lignite, which alternate with 
finely laminated micaceous sandstones, marls, and clays, 
abounding in minute carbonized fragments of fern-leaves, 
with fresh-water shells, and entomostracous crustaceans. 
This series of strata so strikingly resembles in its general 
* Geological Survey of the Yorkshire Coast; by Rev. G. Young; 
1828; p. 197. 
