G:;6 



ICELAND. 



Wd. torn, m a precipice about 2000 feet high. From Indre- 

 ~7' v . holm the Lecls appear horizontal ; but on going round 

 a ff- the mountain we found that they dipped towards the 

 north-east, forming a considerable angle with the hori- 

 zon. From the sea at Intireholm to the foot of the 

 mountain, there is a .flat swamp extending more than a 

 mile. 



To the height of about 800 feet, the mountain of 

 Akkrefell is composed of beds generally from ten to 

 twenty, and sometimes extending to forty feet thick, of 

 varieties of amygdaloid and tuffa. The latter occurred 

 sometimes not more than a foot in thickness, and was 

 interposed between the beds of amygdaloid. When it 

 was so thin, it much resembled red sandstone. While 

 scrambling among the loose stones, we had met with 

 quantities of slags, for which we were at a loss to ac- 

 count, as we had been told that nothing like lava existed 

 on or near this mountain. Its appearance indicated no- 

 thing volcanic ; and our surprise on finding any un- 

 doubted productions of fire in such a place was in- 

 creased, when, at the height above mentioned, we saw 

 the under part of a bed completely slaggy, and bear- 

 ing the most unequivocal marks of no slight operation 

 of fire ; and on continuing to ascend, we found every 

 bed, excepting those of tuffa, one of which was at 

 least forty feet thick, presenting the same appearances, 

 and many of them- having an amygdaloidal character. 

 Our astonishment was not lessened on discovering a 

 vein of greenstone, about four feet thick, cutting these 

 beds, and having a vitreous coating on its sides, which 

 seems to be common to all the veins of the country. 

 Similar beds occur in the mountains of Esian, where the 

 most important fact connected with them was found in 

 a mass of slag which contained calcareous spar." 



The same traveller, in a memoir concerning the Fa- 

 roe Islands, printed in the 7th volume of the Edinburgh 

 Transactions, thus speaks of the trap rocks of that 

 country. " The surfaces of many lavas which I passed 

 over in Iceland, were not unlike coils of rope, or crum- 

 pled cloth ; an appearance which we should expect to 

 be assumed by any viscid matter in motion. On our 

 first visit to the island of Naalsoe, we observed the sur- 

 face of a bed of amygdaloid, which had been exposed 

 to a considerable extent by the removal of the bed above, 

 exhibiting an exact picture of the lavas I had seen in 

 Iceland. At first sight, this discovery fixed instanta- 

 neous conviction on the minds of those who were with 

 me, some of whom had never seen lava, that heat must 

 have caused the appearance before us. We brought 

 away a number of specimens, which are now before 

 the Society, and which speak a language not to be mis- 

 understood. We afterwards discovered varied examples 

 of this crumpled surface in different parts of the coun- 

 try. In the vicinity of Eyde, in Osteroe, there were 

 many instances in which the matter appeared as it', in 

 a viscid state of fusion, it had flowed and spread itself 

 out." These appearances were seen in different parts 

 of Faroe. Mr Allan, in the same volume, has*described 

 the individual minerals found in the trap of Faroe, 

 and expressed his entire conviction- of its igneous ori- 

 gin ; while, at the same time, he appears at a loss to 

 account for the manner in which heat had operated. 

 Sir George Mackenzie has observed, that "while the 

 great point, the action of heat in the formation of trap 

 rocks, seems to be demonstrated, forming a theory of 

 the manner in which heat has operated in particular 

 cases, is, in a general view, perhaps not absolutely ne- 

 cessary in the present state of geology." Indeed, the 

 farther we advance in the study, the farther we find 





ourselves from the object of our search, while we con- 

 tinue resolved that either heat or water shall be the 

 sole agent. To us, the most reasonable mode for geo- Jll " eralo iH'. 

 logists to follow, appears to be, to consider both heat 

 and water as agents which have been employed in the 

 formation of mineral substances. And we are of opi- 

 nion that a third agent ought to be added, as one which 

 universally and continually operates, we mean gravita- 

 tion. The attraction of cohesion, and electricity, may 

 also with propriety be taken into the service ; and pro- 

 bably to form a just theory, we should give a share to 

 every agent which can in any degree influence the eco- 

 nemy of the globe ; the atmosphere, the motion of the 

 earth, magnetism, &c. But at present we must refrain 

 from entering on this subject. 



A very remarkable kind of mineralized wood is found 

 on the mountain of Drapuhlid in Iceland. In external 

 appearance, it cannot be distinguished from a mass of 

 charcoal ; yet it is very heavy. Chalcedony is observed 

 in some specimens filling small fissures. When the car- 

 bonaceous matter is burned, a mass remains, which, 

 when bruised, divides into fibres finer than hair, and 

 resembling asbestos ; shewing that the silicious matter 

 had penetrated into the most minute pores of the wood. 

 This substance occurs in a bed of tuf lying under pearl 

 stone. This last substance occurs of a light gray colour, 

 and also dark green approaching to pitch stone. It 

 was found also forming the principal ingredient in a 

 variety of tuf not before described. " It is composed 

 chiefly of masses of black pearlstone, imbedded in a 

 dull blackish green matrix. It contains also masses of 

 amygdaloid, and we found a few nodules of pyrites in 

 it, coated with pitch coal. Pitchstone occurs -at Houls, 

 ami on the west side of the mountain called Baula. 



The surturbrandt of Iceland has not been seen in $ urtm ^ 

 situ by a mineralogist. It has a great resemblance to brandt. 

 black oak found in lakes and rivers in many countries. 

 But though capable of being shaped into tables and 

 other articles of furniture, it is not in a condition to be 

 cut by a plane into shavings, being somewhat brittle. 



For a description of the individual minerals which 

 occur in these regions, we must refer to the 7th vo- 

 lume of the Edinburgh Transactions, and to Sir George 

 Mackenzie's Travels. The silicious depositions of the 

 Geysers and other hot springs are very interesting, but 

 are now well known to mineralogists. 



The volcanic formation of Iceland is perhaps the Vo lcanic 

 most extensive in the world, covering an extent of at formation, 

 least 60,000 square miles. Sir George Mackenzie dis- 

 tinguishes three formations, which are ascribed to the 

 action of internal heat. The oldest is that already de- 

 scribed as submarine lavas, which resemble trap rocks 

 more nearly both in position and structure, than any 

 other ; and which he supposes to have flowed at the 

 bottom of the sea. The next is a class of lavas to 

 which he has given the name cavernous, from its con- 

 taining numerous cavities, some of them very exten- 

 sive. This is supposed to be formed of rocks which 

 have been subjected to subterraneous heat, but not re- 

 moved from their original place. Many of the appear- 

 ances presented by this class seem to warrant this con- 

 elusion in regard to its mode of formation ; but the con- 

 jecture is thrown out merely to attract the attention of 

 future observers of volcanic countries. The la.st is the 

 ordinary erupted lava, including ejected substances. 

 Perhaps there is no field in which the investigation of 

 the operations of heat could be carried on with greater 

 facility than in Iceland, the rocks are so well exposed 

 to view. But the (shortness of the season in which tea- 



