Illustrations of the Huttonian Theory of the EarthPlayfair, John
Science
Illustrations of the Huttonian Theory of the Earth
Playfair, John
Geology; Hutton, James, 1726-1797. Theory of the earth
Description of this granite, § 288. Pierre graphique of M. Patrin
not perfectly the same with that of Portsoy, § 289. Quartz
crystallized in the pierre graphique, § 290. Instances of quartz
crystallized in other granites. In that of St Agnes in Cornwall,
§ 291. Whether this crystallization is only found in secondary
granites, § 292.
3. Stratification of Granite.
p. 326
Question stated concerning the stratification of granite, § 293.
Remarkable examples of stratified granite at Chorley Forest,
Leicestershire, and at Fassnet _Water_ in Berwickshire, § 295.
Stratification of Mont Blanc, and the Aiguilles of Chamouni
maintained by Saussure, § 296, 297. Seems nevertheless doubtful,
§ 298. In the granite mountains of Arran doubtful; § 300.
Explanation of the stratification of granite in this theory, §
301. If granitic veins were found proceeding from real granitic
strata, they could not be explained on the principles here laid
down, § 302. No such veins have been discovered, § 303. Answer to
an objection made to the igneous origin of granitic mountains, §
304, 305. Of the proportion of the earth's surface occupied by
granite rocks, § 306. Not exceeding a ninetieth part, § 307, 311.
Extent of granite in Scotland erroneously estimated by Dr Hutton,
§ 312. Amounts perhaps to a twenty-fourth of the whole surface, §
313. Observations on Mr Kirwan's opinion, § 314.
NOTE XVI.--Rivers and Lakes.
p. 350
The rivers have hollowed out the valleys, § 315. Illustration
from the course of the Danube, § 316. Courses of many rivers
retain marks of having consisted of a series of lakes, § 317,
318. Filling up and draining of lakes, § 320. Instances from
the lakes in Cumberland, § 321. Lake of Geneva, § 322. Lakes in
North America, _ib._ Cataracts, § 323. Difficulties in explaining
the generation and continuance of lakes exemplified in that of
Geneva, § 324. Attempt to resolve these difficulties, § 325, 326,
327, 328. All lakes not equally subject to them, § 329. Wasting
of the land by the rivers, proved from the mouths of rivers on
bold coasts, § 330. Examples from Cornwall, § 331.
NOTE XVII.--Remains of Decomposed Rocks.
p. 371
Plain of Crau, § 334. Its gravel from the decomposition of
pudding-stone, § 385. Same true of much of the gravel in this
island, § 337, 338. Mount Rigi in Switzerland the remains of a
body of pudding-stone, § 339. Measure of the destruction in the
stratified rocks sometimes, afforded by the unstratified, § 340,
341. Rate at which the elevation of mountains has been supposed
to decrease, § 342.
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