824 



THE WONDERS OF GEOLOGY. Legt. VIII 



melted matter ; the various utensils and works of art, as 

 you may observe in the lamps, vases, beads, and instru- 

 ments in the British Museum, exhibit no appearance of 

 having been exposed to the action of fire. Even the delicate 

 papyri appear to have sustained more injury from the 

 effects of moisture and exposure to the air, than from heat; 

 for they contain matter soluble in naphtha, and are in fact 

 peat in which bituminization has commenced.* In Pompeii, 

 the sand and stones are loose and unconsolidated ; but in 

 Herculaneum, the houses and works of art are imbedded in 

 solid tuff, which must have originated either from a tor- 

 rent of mud, or from ashes moistened by water. Hence 

 statues are found unchanged, although surrounded by hard 

 tuff, bearing the impressions of the minutest lines. The 

 beams of the houses have undergone but little alteration, 

 except that they are invested with a black crust. Linen 

 and fishing-nets, loaves of bread with the impress of the 

 baker's name ; even fruits, as walnuts, almonds, and chest- 

 nuts, are still distinctly recognizable. The remarkable 

 preservation, for nearly two thousand years, of whole cities, 

 with their houses, furniture, and the most perishable sub- 

 stances, imbedded in volcanic matter, may be compared to 

 those geological events, by which the forests of an earlier 

 world, and the remains of the colossal dragon-forms which 

 inhabited the ancient lands and waters, have been accumu- 

 lated beneath the deposits of innumerable ages. 



12. Conservative effects of Lava Currents. — 

 Although no vestiges of animals or plants are likely to be 

 found in volcanic products that have been in an incandescent 

 state, yet so slow is the conducting power of many earths, 

 that beds of shells, and vegetable remains, may be overflowed 

 by streams of molten lava without injury, if protected by 

 even a thin covering of sand or other non-conducting 

 material. In like manner the ancient basaltic lavas have 

 * Dr. Macculloch. 



