BABBAGE ON THE TEMPLE OF SERAPIS. 193 



in succession, the inner layers being rather more crystalline than the 

 outer. 



The exterior surface shows a number of large striae extending in 

 a vertical direction, and in some parts presents the appearance of 

 being mammellated. 



Mr. Faraday informs me that "this deposit consists principally of 

 carbonate of lime. A little sulphate of lime is present, and also a 

 little oxide of iron with silica and alumina, but all these together do 

 not probably make more than four or five per cent. I can find no 

 magnesia, nor any but the minutest trace of muriates." 



Of the Strata in which the Temple was imbedded. 



41. At the north corner of the temple on the outside, behind the 

 chamber D 4, I found a good section of the bed by which the temple 

 was covered up. It is about 20 feet high, and I regret that al- 

 though I measured and noted the thickness of some of the strata 

 and brought away specimens, yet I did not examine them with that 

 minuteness which my subsequent reasonings upon the facts convince 

 me they well deserve. 



No. 1, commencing from the present surface of the adjacent 

 country, is a bed which appears to be a modern accumulation of 

 rubbish. The foundation of a stone wall penetrates this bed, but 

 does not enter the next. 



No. 2 is a bed of coarse sand apparently volcanic, and of pebbles 

 mixed with sea shells : it is about 1 foot 3 inches thick, and resembles 

 No. 6, except that it has shells and contains more crystals. 



No. 3 is a dark grey sand about 6 inches ; it is almost entirely 

 composed of crystals, and is clearly volcanic. 



No. 4 is composed of coarse sand and pebbles, and is about 8 inches 

 thick. 



No. 5 is composed of waterworn brick, sea-shells and shingle. In 

 it occur masses of rolled brick-work, some of them measuring a foot 

 in each direction. Serpulaeare attached to them, and in their inter- 

 stices shells are found sometimes in good preservation. This bed 

 also contains portions of mosaic, and is about 1 foot 8 inches thick. 



No. 6, or the lowest bed, is probably volcanic tuff. It resembles 

 it in colour, and in the roughness and angularity of its aggregated 

 grains ; in the silky pumice-like appearance of some parts, and in con- 

 taining very minute black grains, possibly hornblende and specular 

 iron. It is pulverulent like that above Pompeii. I did not observe 

 any shells in it, nor are there any indications of its having been rolled 

 by the sea, although in one part of the section there was an efflores- 

 cence of salt. 



I believe these beds succeed each other, but unfortunately I 

 omitted to measure their height above the pavement of the temple, 

 and I only possess specimens of Nos. 2, 3 and 6. 



Various Observations. 



42. The water of the Mediterranean enters the temple by a chan- 

 nel A A of masonry, about 3 feet deep and about ly foot wide. 



