256 
THE MEDITERRANEAN NATURAL ' ST 
but as no sections were in the ici nit it a -as not 
possible to determine its thickness. Judging, 1 
however, from a fragment which I detr in • 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 j 
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 j 
well defined patches of calcite having a semi- 
radiated structure. 
The insoluble residue that resulted after treat- 
ment with hydrochloric acid was chiefly composed 
of siliceous particles, and of fiocculent, carbona- 
ceous 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 refe- 
rence 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 ou the cliff face its thick- 
ness was not shown. 
Neither of the patches were of any great extent, 
and would not of themselves be sufficient to ac- 
count 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 and veins that formerly occurred in ! 
those portions of the Lower Coralline Limestone j 
that were broken up when the upper deposits of 
the district were swept away. As I shall after- 
wards show when describing the occurrence of 
similar veins in the Gozitan beds, this black cry- 
stalline variety of the basement rock is still very 
common in the upper layers of 'that formation. In 
the Malta district to which I have just been 
referring these upper layers have been completely j 
swept away, and nearly all traces of black veins 
have thus been obliterated. 
Iu Gozo its mode of occurrence may be studied 
to the best advantage in the Lower Limestone 
quarries that are situated on the southern coast 
in close proximity to the church •: the Madonna 
della Kala, and immediately opposite the islet of 
Comino. (1) Fragments of a red as well as of a 
black variety are strewn around the hillsides in 
great number, while quantities of red and of black 
shippings are to be found intermixed with the 
debris of the quarry. 
The sections that the quarrymen have cut, show 
that both varieties occur in thin irregular veins of 
from one foot to three feet iu thickness, and from 
ten to twelve feet in length; or as irregularly 
shaped patches having diameters ranging from 
three to eight feet. In some instances several 
smaller veins ramify from the main seam, and 
pursuing an irregular course of a few feet in a 
horizontal direction, they break off abruptly. 
It is in and around the “Scutella” seam which 
forms the capping of the L over Limestone, that 
the greatest number of veins and patches seem to 
occur : they are, however, found iu the underlying 
divisions also. 
The varieties of the rock vary greatly in 
their lithological aspects in different parts of the 
bed. In the upper divisions t] 
texture and granitic appearance, unfit their fossil 
contents consisting of Orbit •/ 'es, Echini and spin-.* 
are plainly disternable; but in the lower parts, 
their close, fine grain causes them to exhibit an 
exceedingly homogeneous appearance. Another 
locality in which the red variety is extensively 
developed is the bottom of the valley which is 
situated midway between Ras-el-Hecca and Uied 
tal Assiri on the northern coast of Gozo. The 
torrent that tears its way down the bed for a few 
occasional hours during the rainy season has there 
laid bare the basement rock, and has exposed a 
large patch of bright, red limestone that answers 
in every particular to the rock of which the 
numerous fragments that lie scattered over the 
surrounding slopes, are composed. 
In common with the other rock fragments with 
which the country is strewn, there can be no doubt 
but that these black and red varieties were derived 
(J) Mi/ attention cctol i» it a occurrence 
in this locality by Prof. X. Toydafrro. 
