Ch. VI.] TEERACES IN SICILY. 77 



example of this configuration occurs near the town of Melilli, as 

 seen in the annexed view (fig. 95). In the south of the island, near 

 Spaccaforno, Scicli, and Modica, precipitous rocks of white limestone, 

 ascending to the height of 500 feet, have been carved out into similar 

 forms. 



This appearance of a range of marble seats circling round the head of 

 a valley, or of great flights of steps descending from the top to the bot- 

 tom, on the opposite sides of a gorge, may be accounted for, as already 

 hinted, by supposing the sea to have stood successively at many different 

 levels, as at a a, b b, c c, in the accompanying fig. 96. But the causes 

 of the gradual contraction of the valley from above downwards may 



Fig. 96. 



1 



tr zi: 



— ■-.■^ = i == 



still be matter of speculation. Such contraction may be due to the 

 greater force exerted by the waves when the land at its first emergence 

 was smaller in quantity, and more exposed to denudation in an open 

 sea ; whereas the wear and tear of the rocks might diminish in propor- 

 tion as this action became confined within bays or channels closed in on 

 two or three sides. Or, secondly, the separate movements of elevation 

 may have followed each other more rapidly as the land continued to rise, 

 so that the times of those pauses, during which the greatest denudation 

 was accomplished at certain levels, were always growing shorter. It 

 should be remarked, that the cliffs and small terraces are rarely found on 

 the opposite sides of the Sicilian valleys at heights so precisely answering 

 to each other as those given in fig. 96, and this might have been ex- 

 pected, to whichever of the two hypotheses above explained we incline ; 

 for, according to the direction of the prevailing winds and currents, the 

 waves may beat with unequal force on different parts of the shore, so 

 that while no impression is made on one side of a bay, the sea may 

 encroach so far on the other as to unite several smaller cliffs into 

 one. 



Before quitting the subject of ancient sea-cliffs, carved out of lime- 

 stone, I shall mention the range of precipitous rocks, composed of a 

 white marble of the Oolitic period, which I have seen near the northern 

 gate of St. Mihiel in France. They are situated on the right bank of 

 the Meuse, at a distance of 200 miles from the nearest sea, and they 

 present on the precipice facing the river three or four horizontal grooves, 

 one above the other, precisely resembling those which are scooped out 

 by the undermining waves. The summits of several of these masses are 

 detached from the adjoining hill, in which case the grooves pass all 



