THE MEDITERRANEAN NATURA LIST 
209 
from the western, with a deep-water fauna that 
had migrated from the eastern-basin (I). 
Comparing these facts with those that the 
nodule seams themselves now supply us with, it 
seems reasonable to suppose, that each seam marks 
a period at which one of these physical changes 
in the sea bed took place, and which, by altering 
the conditions most favourable to the then existing 
marine flora and fauna, it caused all organic life 
then existing in the waters to die off suddenly 
and to leave their remains distributed in thick, 
regular layers over the sea bed. 
It was from these remains that the phosphoric 
acid was derived, which now enters so largely 
into the composition of the rock. 
The origin of the nodules themselves is more 
obscure. Alluding to this subject Dr. John Murray 
remarks that the nodules found in the Malta 
beds are pecisely similar to the phosphatic nodules 
that were dredged from modern sea beds during 
the “Challenger” cruise, and he is of opinion, that 
both were formed in situ at the bottom of the sea. 
The following table gives the result of the 
analyses of the Maltese nodules, made in 1890 
and 1891 by Dr. John Murray and Prof. J. F. 
Blake respectively. 
From these tables it will be seen that the 
amount of phosphoric acid contained in the 
matrix is so small, and the amount of calcium 
carbonate is so great, that were the matrix not 
separated from the nodules it would lower the 
market value of the product to such an extent as 
to render it worthless. 
This separation may however be easily effected 
owing to the soft character of the limestone in 
which the nodules occur. 
Several experiments have already been made on 
a small scale the modus operand! of which was as 
follows. Masses of the phosphate rock were bro- 
ken up into small blocks averaging from 3 to 4 
inches in diameter, after which they were trans- 
ferred to a kiln for calcination. When ready, 
the material was subjected to a powerful stream 
of water and screened by which means the nodules 
were obtained free from the matrix, the former 
remaining in the sieve, and the latter passing 
though it as quick-lime. The nodules were then 
dried and crushed into a fine powder, which on ana- 
lysis gave 41. 5 % of phosphate of lime, with no 
trace of iron, and but slight traces of alumina. 
Dr. Murray’s Analysis. 
Sulphate of Lime Ca S0 4 2. 26 
Carbonate of Lime Ca C0 3 47. 14 
Phosphate of Lime Ca a 2 P0 4 38. 34 
Alumina AL O., 5. 98 
Oxide of Iron Fe 2 0 3 trace 
Residue ' , 6. 08 
99. 80 
Prof. Blake’s Analysis. 
Sulphate of Lime 
1 . 
97 
Carbonate of Lime 
51. 
12 
Phosphate of Lime 
31. 
66 
Alumina etc. (indeterm.) 
10. 
55 
Silica 
3. 
83 
Moisture 
- 
87 
100 . 
. 00 
In Prof. Blake’s analysis the nodules and equal 
parts of the interstital cement were taken, whereas 
Dr. Murray took the nodules only. 
The following is the analysis of the interstital 
cement. 
Carbonate of Lime (Ca CO. ; ) 86. 69 
Phosphate of Lime (Ca. ; 2 P0 4 ) 1 . 24 
Sulphate of Lime (Ca S0 4 ) 0. 07 
Alumina (Alo 0 ;J ) 1 . 28 
Insoluble in dilute H Cl. 9. 87 
99. 15 
This shows the Malta rock to be but of a low or 
medium-grade, yet it is much richer than the 
Belgian phosphates that are now in the European 
market and that do not average more than 29 % of 
phosphate, with 63 % of lime. It is therefore 
hoped that some means may be devised whereby 
the Maltese phosphates may be put on the Italian 
market as there is at the present time a brisk 
demand in that country for low-grade rock. 
(1) The Maltese Fossil Ecliinoidea by J. W. 
Gregory, F.G.S., Froc. Roy. Noe. No. di. Vol. 36, 
