No. II. — Herculaneum, Pompeii, and Stabicc. 127 



has flowed from the mountain within the Hmits of history be- 

 fore the year 1036. The heat of the Hqiiid mass is proved 

 by the carbonization of the timbers, corn, papyrus rolls, and 

 other vegetable substances which have been discovered ; and 

 that it dried from a fluid state is rendered in the highest de- 

 gree probable, from the remarkable appearance which may at 

 present be seen in one of the galleries excavated behind the 

 theatre, of an impression in the solid mass sharply left by a 

 mask which had been accidentally buried *. A similar illus- 

 tration is still preserved in the museum at Naples, where is a 

 piece of tufa containing a perfect cast of a portion of the hu- 

 man body. I have related a similar fact of the most recent 

 formation, the tufa of 1822, in the last number of these no- 

 tices -I* ; a specimen of which, in my possession, contains a 

 complete impression of a leaf of a tree, — a convincing proof of 

 the great liquidity of the substance. 



Regarding the particular structure of the mass which covers 

 the city of Herculaneum, we may, in the first place, remark its 

 great thickness. Below Resina, the modern village, it is 125 

 palms (of about 11 inches each,) in depth, and above the thea- 

 tre, 85 French feet. Delia Torre informs us, that at the 

 deepest part it is divided by strata of white volcanic ashes, and 

 above the tufa there are 12 or 14 palms of common soil, 

 containing ancient tombs, and covered again by a modern, 

 true siliceous lava, (lava di pietra dura.) This, as far as I 

 know, is the most distinct statement of the strata above Her- 

 culaneum. The nature of the tufaceous substance is rather 

 peculiar. When first excavated, it is soft and easily worked, 

 but acquires a considerable degree of induration on exposure 

 to the air, though if it becomes nearly dry it is friable. In 

 structure it is porous, and contains a great number of imbed- 

 ded masses of various sizes, and decomposed mineral substan- 

 ces, (farinaceous leucites.?) but more particularly abundant 

 small black particles have been observed, J which appear to be 



* This appearance existed as far back as the time of Sir William Hamil- 

 ton, who compares its sharpness to that of a cast in Paris plaster contract- 

 ed by cooling. 



+ In No. xviii. p. 206. 



t Delia Torre Storia del Vesuvio, § 119. Lalande, vii. 479. 



1 



