18 
NODULE BEDS. 
determined. This has been done in the subjoined analyses which 
at the same time represent their their detailed composition : — 
Detailed Composition op Suppolk Copbolites. 
No. 1. 
No. 2. 
Moisture and water of combination with a trace 
of organic matter 
- 
- 
5*76 
2*53 
Lime - - - 
- 
- 
40*70 
38*20 
Magnesia - 
- 
- 
•34 
1-34 
^Phosphoric acid - 
- 
- 
28*32 
24*24 
Oxide of iron 
- 
1 
r4.81 
Alumina - - 
. 
/ 
^ Of 
13-72 
^Carbonic acid 
. 
5*08 
5*37 
Sulphuric acid 
- 
*87 
1*40 
Potash 
- 
*78 
*56 
Soda 
- 
*25 
1*18 
Chlorine - - . 
- 
traces. 
•07 
Fluorine and loss - 
- 
3*02 
4-31 
Insoluble siliceous matter 
- 
10-01 
12*27 
100-00 
100-00 
ia) Equal to tribasic phosphate of lime (bone-earth) 
61*30 
52*52 
(5) Equal to carbonate of lime 
- 
- 
11*64 
12*20 
'‘No. 1, it will be seen, is a very superior sample : No. 2 
represents a good average sample of Suffolk coprolites. In two 
other samples, in which the amount of insoluble matter and 
phosphoric acid alone was determined, I find :— 
No. 1. No. 2. 
Insoluble silicious matter - - » - 12*56 11*05 
Phosphoric acid ----- 23*48 24*26 
Corresponding to bone-earth - - 50*87 52*56 
It should be remembered that although phosphates have 
generally been worked only at the base of the Bed Crag, they 
may yet be profitably dug also at the bottom of the Coralline 
Crag. Prof. Prestwich says that “ it was only at one small pit 
[at Sutton], and there for a short time that the bed of phosphatic 
nodules at the base of the Coralline Crag was worked."' He also 
tells us that “ the condition ... of the bones at the base of 
this Crag is precisely of the same character as that of those at the 
base of the Bed Crag,” 
