362 John H. Coolie — Black Limestones of Malta. 



jet-black lustre, occur at different depths intermixed with boulders 

 and fragments of other colours, eiglity per cent, of which ai'e at 

 once recognizable as having been derived from the formation out of 

 which the creek has been formed. They generally lie with their 

 longer axes in a horizontal direction, forming well-defined layers of 

 several feet in thickness, alternating with beds of a rich red soil, 

 containing the remains of several extinct species of elephants. 



It was to this part of the island that I first directed my attention 

 in my search for the origin of the bed from whence these boulders 

 and pebbles had been derived, as, owing to the great amount of 

 denudation to which the country around had been subjected, the 

 whole of the beds, that had formerly overlain the basement rock, 

 had been completely swept away, and the Lower Coralline Lime- 

 stone had been laid bare over an area of several square miles in 

 extent. The first evidence of the black limestone occurring in situ 

 appeared on the road between Benhisa and Uied el Mista. The 

 exact spot is situated directly opposite to II Mara, at a distance of 

 about 400 yards from the sea cliffs. It consists of a patch of black 

 crystalline marble, which is similar in every respect to the limestone 

 of which the boulders and pebbles are composed. The patch extends 

 h^ilf-way across the road, and on the off side a cart-rut has been 

 formed in it to a depth of eight inches. It occurs in division h of 

 the Lower Coralline Limestone, but as no sections were in the 

 vicinity it was not possible to determine its thickness. Judging, 

 however, from a fragment which I detached at the bottom of the 

 rut, and which showed a gradual transition of the black into the 

 characteristic yellow variety of the formation, it is not probable that 

 it is more than a foot. I broke off several pieces and made sections 

 of them, as well as of several of the pebbles from the Benhisa Creek, 

 which is not more than a mile away. 



An examination under the microscope showed the specimens from 

 both localities to have a granular texture, with here and there 

 numerous well defined patches of calcite having a semi-radiated 

 structure. 



The insoluble residue that resulted after treatment with hydro- 

 chloric acid was chiefly composed of siliceous particles, and of 

 flocculent, carbonaceous matter which remained in suspension in 

 the solution for some considerable time. Both were hard, compact, 

 and crystalline ; and chemical analysis revealed the presence of 

 sulphide of iron. The specimens were evidently identical. About 

 one mile from this spot, and situated about 200 yards to the west 

 of Ghar Hasan's Cave on the same coast, there is another patch or 

 vein, which is similar in every respect to that to which reference 

 has just been made. It occurs on the cliff edge, and at the western 

 extremity of the first wall which is met with after leaving the cave. 

 It is but small, having a diameter of four feet only, and as it does 

 not abut on the cliff" face its thickness was not shown. 



Neither of the patches were of any great extent, and would not 

 of themselves be sufficient to account for the quantities of blocks 

 and fragments that lie scattered over the rock surfaces in their 

 vicinity. It is probable that they are the remnants of the patches 



