284 



THE WONDERS OF GEOLOGY. Lect. III. 



I found a small wood of petrified trees in a vertical position; or rather, 

 the strata were inclined about 20° or 30° to one point of the trees, and 

 70° to the other ; that is, before the tilt, they were truly vertical. The 

 sandstone consists of many horizontal layers. Eleven of the trees 

 are perfectly silicified, and resemble the dicotyledonous wood which I 

 found at Chiloe and Conception ; the others, from thirty to forty in 

 number, I only know to be trees from the analogy of form and position ; 

 they consist of snow-white columns of coarsely crystallized carbonate 

 of lime. The largest trunk is seven feet in circumference. They are 

 all close together, within one hundred yards, and about the same level ; 

 no where else could I find any. It cannot be doubted that the layers 

 of fine sandstone have quietly been deposited between a clump of trees, 

 which were fixed by their roots. The sandstone rests on lava; is 

 covered by a great bed, apparently about one thousand feet thick, of 

 black augite lava; and over this there are at least five grand alter- 

 nations of such rocks, and aqueous sedimentary deposits, amounting 

 in thickness to several thousand feet. According to my view of these 

 phenomena, the granite, which forms peaks of a height probably of 

 14,000 feet, has been fluid in the tertiary epoch ; strata of that period 

 have been altered by its heat and are traversed by dykes from the 

 mass, and are now inclined at high angles, and form regular or com- 

 plicated anticlinal lines. To complete the climax, these same sedi- 

 mentary strata and lavas are traversed by very numerous true metallic 

 veins of iron, copper, arsenic, silver, and gold, and these can be traced 

 o the underlying granite. A gold mine has been worked close to the 

 clump of silicified trees ! " 



58. Tertiary saliferous deposit. — Not only coal, 

 but even extensive beds of rock salt occur in the tertiary 

 system. The celebrated salt mines of Galicia, of which 

 M. Boue* has given an interesting description, belong to 

 this epoch. The deposit is nearly 3000 yards long, 1066 

 broad, and 280 yards deep. The upper part of the mine 

 consists of green salt, with nodules of gypsum in marl. 

 The salt contains in some places lignite, bituminous wood, 

 and shells. In the lower division are beds of arenaceous 

 marls, with lignite, impressions of plants, and veins of salt ; 

 coarse sandstone, with vegetable remains ; aluminous and 



* Journal de Geologic. 



