ROCK. 



in Saxony, where the order of fucceflion presented con- 

 fiderable regularity, concluded that each principal rock 

 constituted what he called a univerfal formation, or was 

 originally fpread round the globe, and that thefe formations 

 fucceeded in a determinate order, encircling each other like 

 the coats of an onion. 



More recent and extended obfervations do not confirm 

 this conclufion to the full extent to which it was carried by 

 the German geologifts. Of the thirteen rocks which he 

 clafTes as primary, fome arc entirely unknown in various 

 parts of the world, and one of them, the topaz rock, has 

 hitherto been found only in Saxony. Many of the fecondary 

 rocks, which occupy a confiderable fpace in Europe, are no 

 where met with in North or South America. In Afia, 

 we are informed by travellers, that a range of mountains, 

 compofed of jafper, extends far more than a thouiand 

 miles through the eallern parts of Siberia, including Gore 

 ifland, between that country and America. A geologilt, 

 who refided in Siberia, might be difpofed to regard jafper 

 as the principal rock-formation in the world, as it extends 

 over a far greater fpace than the diltridts in which Werner 

 laid the foundation of his fyllem ; on the contrary, in many 

 parts of Europe, jafper is little known, nor is it even enu- 

 merated among the principal rock: of Werner. 



Mr. Bakewell, in his " Introduction to Geology," 

 admits only three principal rocks in the clafs of primary ; 

 in which arrangement he is fupported by D'Aubuillon, an 

 intelligent difciple of Werner, who, on a recent examination 

 of the mountains in the department of Mont Blanc, found 

 that many of the rocks, heretofore regarded as primary, 

 contain fome organic remains ; hence lie admits of one pri- 

 mary formation only, which includes granite, gneils, and 

 mica-flate. 



Brongniart, a celebrated French mineralogilt, has more 

 recently declared his opinion, that it is no longer poflible to 

 admit the clarifications eltabliflied by Werner. " At the 

 time when thefe were formed, they rendered an eflential 

 fervice to geology, and created the fcience ; but new obfer- 

 vations mult produce correfpondent changes in the denomi- 

 nations and fyftem of arrangement." Journal des Mines, 

 May 1814. Without adhering to fyftems, further than 

 they are fupported by fafts, we coniider granite as the 

 lowed rock that is generally met with in alpine diuritts. 

 Granite is frequently covered by a rock called gneifs, a kind 

 of ilaty granite ; on this occurs micaceous ichid, or mica-flate. 

 For the characters of thefe rocks, fee Granite, Gneiss, and 

 Mica-oVj/c 



Thefe three rocks are frequently obferved graduating 

 intoeacli other, and fometimes alternating. The lubllances 

 which compofc them appear to have been in a fluid ltate, and 

 to have united in various forms and proportions ; and cer 

 tain caufes have given to the outer part a fchiltole or flaty 

 Itru&ure. The gneifs and mica-flate are generally moulded 

 over the granite, with the fame elevations and depreflions. 

 Beds of other rocks, particularly of granular lime-ltone, 

 hornblende rock, and terpentine, occur occafionally in thefe 

 rocks, with beds and veins of metallic ores. 



The higliefl mountains on tin' continents of Europe and 

 Afia are compofed of thefe rocks. Mont Blanc is 15,680 

 feet above the level of the fea. 



Granite rocks are in fome in (lances immediately covered 

 by (late; and in others, fecondary ftratified rocks reil upon 

 granite, without the intervention of rocks which ufually ac- 

 company it. More commonly, mountains of flate, or the 

 coarfe kind of flate-rock, called by the Germans grey-wae ke 

 and grey-wacke flate, c»ver the mica-flate and pieiffl, fm- 



menfe beds of lime-done frequently accompany this kind of 

 flate, in which the remains of marine animals, principally zoo- 

 phytes, appear, but different from any known exiitmor fpecies. 

 A very thick bed of iand-ftone, frequently coloured red by 

 the oxyd of iron, often accompanies the coarfe (late. It 

 is called by Werner the old red land-Hone, and is fucceeded 

 by beds of lime-itonc, in which the organic remains of zoo- 

 phytes and fhcll-iifh are more abundant : thefe are the lowed 

 rocks in which metallic veins ufually occur. Over this lime- 

 done we meet witli numerous llrata of argillaceous and filice- 

 ous fand-dones, and foft flate or (hale, abounding with imprel- 

 fions of vegetables, impregnated with bituminous and carbo- 

 naceous matter, and alternating frequently with beds of coal. 

 Thefe fecondary ltratified rocks, called by the Germans 

 floetz rocks, will be more particularly defcribed under the 

 article Strata. 



Again, over the drata containing coal, or more properly 

 on the boundary of thefe ftrata nearelt the fea, we meet 

 with calcareous ltrata containing the remains of marine 

 animals, but different from thofe found in the lower rocks. 

 Thefe calcareous ltrata confilt of calcareous fand-ftone, roe- 

 ftone, and chalk. See RoE-Stone, and Chalk. 



It is remarkable that chalk, which is extenfively fpread 

 over the fouthern counties ol England, and the oppolite 

 coalt of France, and in many of the countries adjoining 

 the Baltic, is unknown in North and South America, 

 and various parts of the world. Over the chalk are found 

 thick beds of clay and fand; and in fome parts of Eu- 

 rope there occurs over thefe a fenes of drata, containing 

 the remains of frefh-water (hells and quadrupeds. See 

 STRATA, in which an account will be given of the frefh- 

 water formation of drata in the vicinity of Paris and the 

 fouthern parts of England. This appears to be the latell 

 formation of rock that we are acquainted with, except what 

 is taking place in our own times by volcanic fires. 



It is worthy of remark, that we meet with no organic 

 remains in the lowed rocks we are acquainted with ; that the 

 rocks over thefe contain a few remains principally of marine 

 animals ; that the rocks which immediately cover the marine 

 remains, or the coal fcries, abound in vegetable impreffions 

 and carbonaceous matter ; but we rarely meet with animal 

 remains of any kind in thefe llrata, until we approach nearer 

 the fea-fhore, when other calcareous ltrata occur again, con- 

 taining, almolt exclufively, the remains of marine animals, but 

 different from thofe in the lower rocks. Thefe latter drata 

 confilt of calcareous fand-ilone, roe-Hone, and chalk. See 

 Roe- Stone. 



Beiide the rocks, in which fome order of fuperpofi- 

 tion may frequently be traced, there are other rocks 

 which are thrown over them, apparently by fome great 

 convulfion of nature which has broken the lurface of the 

 globe, and forced them into their pivfcnt poiition, without 

 any regular order of lucccfiion. Thefe rocks conlilt of por- 

 phyry, lienite, trap, or bafalt. From the nature of tj 

 rocks, and the finularity of their poiition with that of vol- 

 canic rocks, many phuofophers have attributed the fame 

 mode of formation to both, and fuppofe that the former 

 have been orignally currents of lavas formed in remote 

 ages. 



Humboldt, who has made more extended obfervations on 

 volcanoes than any philofophervt ho has preceded him, fays, that 

 in the lubllances which have been ejected during volcank 

 eruptions, a gradation may be traced from the more inciei ■ > 

 thole of more recent date, and that the latter have always a 

 nearer relcmblance to the lava I eje&ed at the prefent time. If 

 this obfervation be corroft, it will probably lead to the con- 

 3 D 2 cinliun, 



