4 
and Volcanic Substances. _ 229 
or prismatic, basalt may ve and actually is formed, when 
these masses press against each other : hence, the question 
- of the crystallization of columnar basalt, is not in my. mind 
~fally settled. Phil. trans. 1804, p. 279. 
»» Basalt is, found, sometimes in plains. and in some mea- 
sure conformable to the. supporting stratum—sometimes 
fy filling up yallies—sometimes in compact amorphous, uncon- 
-formable masses—sometimes in figurate and columnar 
Masses, sometimes breaking through the hardest rocks in 
jets, and forming. peaked hills aA knobs—sometimes for- 
-cing up the stratum from below; as at Antraigues in Au- 
vergne, which.1 is. builton curved basalt that supports enor- 
mous masses. of | granite. 2 Soul. § 716. Sometimes in 
) Dykes. reaching to great distances and. of unknown depths, 
disrupting and displacing the strata through which the dyke 
has ivaolently broken. ‘Fhe great coal Dyke of the North 
of England of this kind extends from sea to sea. (White- 
burst-Bakesvell. aN? ‘These Dykes burn, char, fuse, or indu- 
rate all contiguous substances, and break through and dislo- 
cate all metallic veins, as we have already seen. 
Vegetable. organic, remains (Humbold, ) and animal also, 
is rievioc eres Dr. Richardson.) have. occasionally, though 
rarely been found.in, Basalt, adhering 10; or enveloped i in 
“saaateas rye) has charred. wood. 
These.organic remains are not sort in the prismatic or 
figurate, and only io the tabular Basalt, which has met with 
them. in its course. , | have a. shell iabonded’l in the fused 
slag of an, iron, furnace. ‘Metallic “substances, excepting 
- iron, and titaniferous iron, are rarely found in Basalt.” 
Columnar, basalt has been found with water in its cells : 
pethaps owing to-steam, that not escaping, has cooled into 
water.;i Jamieson’s Geognosy, 1808, Ps 186, and 3 Sou- 
lavie.\, 1402. 
Basalt hills are. much subject. to rents and, fede: and 
are often found with fragments. of all. shapes and sizes at 
the, bottom.agd sides; assumaing a | breccious structure ; and 
cemented to, the subjacent, rock as. at La Spisso, Reconro, 
&e.. Ferber:Trav. 
Basalts are frequently. found covering , passing ‘into, and 
connected with, granitic and porphyritic rocks, which Werner 
calls Wacke, Grunstein and Porphyritic ‘shige. so that it is 
frequently in} possible to mark the line of distinction between 
Vor Hl......No. 20. 4 
