208 
THE MEDITERRANEAN NATURALIST 
Tlie second seam is more regular in character. 
' i 
and extends uninterruptedly throughout all of the j 
plateaux. In this respect it offers a marked 
contrast to seam one, which often thins out and 
disappears. 
It consists of an aggregation of irregularly 
shaped nodules, intermixed with which are consi- 
derable quantities of the phosphatized remains of 
molluscs, corallines, echinoderns, crustaceans, 
sharks, whales etc. the whole being firmly bound 
together by an interstital cement composed of 
foraminiferal and other calcareous matter similar 
to that of which the overlying beds are made up. 
It has an average thickness of two feet, and is very 
uniform in its general, physical, and- chemical 
aspects. 
The limestone matrix in which the nodules are 
embedded is of a very soft nature and readily 
disintegrates before the constant and insidious 
attacks of the Scirocco. The nodules contained in 
it, therefore, drop out in considerable quantities 
and falling to the bases of the escarpments they 
become incorporated with the soil of the fields, 
either by the transporting agency of rain or by 
the hoe of the husbandman. 
The third seam is the poorest of the series. 
Its nodules are small, in size and few in number, 
and those that do occur are very irregularly 
distributed. Sometimes this seam consists of two 
or more their layers of nodules none of which 
exceeds three inches in thickness. At Maddalena, 
near the northern extremity of the Great Fault, 
three of these small layers are distinctly shown, 
the upper of which disappears in an easterly 
direction beneath a talus of soil, but to the west 
it thins out and breaks off abruptly. It seems to 
be a purely local development, for it does not 
occur in any other part of the island. 
Between these and the next, or lowest layer, is 
a bed of rock varying in thickness from 50 to 80 
feet, underlying which is the fourth and most 
important seam of the series. The organic remains 
contained in it are more varied, and the nodules 
are larger, richer, and much more numerous. It 
averages 3| feet in thickness, and ranges from 
3 feet to 4j feet. 
The nodules are of a dark chocolate colour, and 
they generally present an exceedingly wrinkled 
and coriaceous appearance. Most of them contain 
one or more fossil organisms around which the 
; phosphate of lime seem to have segregated. The 
numerous sections that I have examined under 
the microscope (1) show the larger nodules to be 
almost entirely mad-; up of the casts of G '• : iys - / 1 
intermixed with a few other foraminifers. 
The phosphatized remains of larger organisms are 
I also extremely abundant. Casts and shells of 
molluscs, echinoderms, and corals; portions of the 
carapaces of turtles, the reeth and bones of telo- 
stean fishes, of sharks, of whales and other mam- 
mals; and innumerable quantities of the casts of 
the pteropods, hyalae, and vagin> lla are a few of 
the many that enter in to the composition of 
this seam. The following calculation shows the 
amount of phosphate of lime that the organisms 
contained in this one bed would yield. 
The bed is persistent throughout Malta ar.d 
Gozo; for my purpose I propose to consider Malta 
only. Estimating the area of Malta at 95 square 
miles, and the average thickness of the seam as 
being 3 feet, we obtain as a result, 7, 945, 344, i h h.) 
cubic feet of rock. 
Supposing that not more than one thousandth 
part of this to be available for quarrying purpo- 
ses, a very modest estimate indeed, we should 
obtain 7,945,344 cub. ft. which at 25 cub. ft. to 
the ton would represent 317,813 tons of a medium 
grade phosphate rock iu the one seam only. 
The origin of these nodules and the phosphati- 
zation of the limestone in which they are embed- 
ded afford us a problem for solution that is of 
great interest. 
The occurrence in the phosphate beds and Globi- 
gerina Limestone of two groups of echinoderms, 
that varied widely in their distribution and cha- 
racters when living, show that the Maltese area 
during the Miocene period was situated on the 
border-line which divided the Mediterranean into 
two parts, each of which differed from the other 
in its physical aspects and conditions. 
The alternate elevations and depressions to 
which the Maltese area was then frequently sub- 
jected led to changes that caused the intermingl- 
ing of the shallow-water fauna that had migrated 
(1) I owe much to the courtesy of Dr. John 
Murray who kindly lent me t/u numerous sections 
of Malta rocks tha t he had had prepared. 
