tOS On tfte CM Caves of the Mwite Tesiaccio at Rome. 



are brought by aqueducts from distances of from fifteen and 

 eighteen to twenty-four miles, all beyond the confines of the 

 Arid Campagna. 



Let us now turn to the little mountain itself, which has such 

 a situation. It is no figure of speech to say that it is com- 

 posed of broken pottery. It is literally and entirely so, without 

 a particle of earth between the fragments ; and in only a few 

 spots on the outside is there a finger's breadth of soil deep to 

 permit a stunted grass to grow, and a few coarse weeds which 

 extend their roots into the fragments. Some excavations in 

 the sides for mending the roads, permit us to see that its inter- 

 nal structure is exactly as I have described, and so loose, that, 

 if you move a small morsel near the bottom, a whole avalanche 

 of the necks, bottoms, and handles of Amphora; descend upon 

 you. The hill is about 160 feet high, and 590 paces, or nearly 

 a third of a mile in circumference. It is evident that the 

 weather must have complete access through the hill, and hence 

 it follows: 1st, That the pots will imbibe and retain the rain 

 water which falls in enormous torrents in winter ; and, 2d, 

 That the wind must have a pretty free access between the cre- 

 vices of the fragments. With regard to the cellars themselves, 

 the one which I entered extended, I suppose, above fifty feet in- 

 to the hill, nor did I observe that the wind came from any par- 

 ticular funnel or chimney prepared for it, but rather appeared 

 to proceed from the sides of the cavern on all hands, which 

 were so loose and full of crevices as to require to be artificially 

 supported. Saussure expresses himself of the same opinion : 

 " Cet air vient lui-meme des interstices, que laissent entreeux 

 les debris d'urnes, d'amphores et d'autres vases de terre cuite, 

 dont cette petite montagne paroit entierement composee." 

 Now, if we attiibute the effect entirely to evaporation, the case 

 seems to stand thus : The exterior air in a state of great dry- 

 ness enters the mountain laterally, passing through it with per- 

 fect freedom, and at the same time acquiring with avidity the 

 humidity presented to it by innumerable surfaces of baked 

 clay, which have already been thoroughly wetted by the rain 

 to the very centre of the mountain ; hence the air must in all 

 cases reach a state of perfect dampness before it reaches the 



caves ; therefore, the depression of temperature depends golel^ 



4 * 



