§ 17. FOSSIL CYCADEiE OF PORTLAND. 387 



vegetation, there being but few trees or shrubs in the 

 whole Island. 



But the most remarkable fact which this section pre- 

 sents, is the position of the trees and plants in the Dirt-bed ; 

 for they are still erect, as if they had been petrified while 

 growing in their native forests, with their roots in the vege- 

 table soil, and their trunks extending into the limestone 

 above {Lign. 84, 4, 3,). As the Portland building stone lies 

 beneath the freshwater strata, which are but little employed 

 for economical purposes, the petrified trees are removed, 

 and thrown by as rubbish. On one of my visits to the 

 island (in the summer of 1832), the surface of a large area 

 of the dirt-bed was cleared, preparatory to its removal, and 

 the appearance presented was most striking. The floor of 

 the quarry was literally strewn with fossil wood, and before 

 me was a petrified forest, the trees and the plants, like the 

 inhabitants of the city in Arabian story, being converted 

 into stone, yet still remaining in the places which they 

 occupied when alive ! Some of the trunks were surrounded 

 by a conical mound of calcareous earth, which had evidently, 

 when in the state of mud, accumulated round the stems and 

 roots. The upright trunks were generally a few feet apart, 

 and but three or four feet high ; their summits were broken 

 and splintered, as if they had been snapped or wrenched off 

 by a hurricane at a short distance from the ground. Some 

 were two feet in diameter, and the united fragments of one 

 of the prostrate trunks indicated a total length of from 

 30 to 40 feet ; in many specimens portions of the branches 

 remained attached to the stem. In the Dirt-bed, there were 

 numerous trunks lying prostrate, and fragments of branches. 



The external surface of all the trees I examined was 

 weatherworn, and resembled that of posts and timbers of 

 groins or piers within reach of the tides, and subjected to the 

 alternate influence of the water and atmosphere ; there are 

 but seldom any vestiges of the bark. 



17. Fossil CtcadejE : — Mantellia. — The fossil plants 

 cc2 



