INTRODUCTORY CHAPTER. xxi 



the eastward of the Piinch-bowl, and in the vicinity of the Great 

 Wood plain, there is not to be found a stone, of any sort what- 

 ever, fit for the purpose of building-. This seems to furnish a 

 further proof, that all that portion of the island is of a different 

 formation from the other parts. 



On the surface of Ladder Hill are some beds of basaltes, pro- 

 ducing flaky stones of extreme hardness. These lie horizontally, 

 and when quarried, yield flags of from six to twelve superficial 

 feet, and from four to ten inches in thickness. They are also 

 sonorous; and as they require only to be squared, they are 

 admirably adapted to the flooring of warehouses, granaries, 

 and other buildings. In blasting some of the basaltic beds on 

 Ladder Hill, both sides of the septa, or cracks, were sometimes 

 covered with figures, apparently of metal ; of a bright silver 

 colour, , beautifully representing trees and other objects of 

 landscape. 



On the western side of High Knoll there are quarries of a very 

 different description. They produce a stone very much resem- 

 bling the Tufa I have seen in Sicily. Indeed this stone, and the 

 small pieces of very light pumice which are scattered at the 

 northern base of High Knoll, and upon many parts of Ladder 

 Hill, are the only sorts that bear the smallest resemblance to the) 

 productions of Etna, Strombolo, and Vesuvius. I had a com- - 

 plete collection of these in my possession, which enabled me to 

 make the comparison. 



The tufa, or red-stone of St. Helena, is of a brownish red 

 colour. It is rather soft when taken out of the quarry, but 

 hardens by exposure to the air, It has been used successfully 

 in building ; and in forming a water-course for supplying the 

 garrison of Ladder Hill, from the springs at Plantation-house ; 

 and from the tank at High Knoll.* 



* Parti. Sec. XXIX. page 199, 



