1890-91.] Mr J. Y. Buchanan on Deep-Sea Deposits. 135 
Near the African coast the amount of C0 2 varies between 8 and 
10 per cent. It increases with distance from the land, being no 
doubt less masked by land debris. The maximum 20-97 of C0 2 
(47 T 7 CaC0 3 ) is found on the Balearic Bank. The depth here 
was only 782 fathoms, and the land drainage is insignificant. 
Table Y. Treatment with Hydrochloric Acid. — (A.) A weighed 
quantity of the substance was placed in a porcelain basin and 
100 c.c. of 20 per cent, hydrochloric acid added. The basin was 
placed on a water-bath and evaporated to dryness. It was then 
placed on an air-bath and heated so as to convert any soluble silica 
into the insoluble form. Then it was treated with hydrochloric 
acid and filtered. The precipitate was weighed, and called the 
“ residue.” 
(B) The “ residue ” was fused with potassium sodium carbonate, 
and the silica determined in the usual way. 
Table Y. — Determination of the Residue Insoluble in 20 per cent. 
HC1, and of the Total Silica. 
No. of 
Sample. 
Weight 
of Sample 
taken 
(grammes). 
Weight of 
Insoluble 
Residue 
(grammes). 
Per cent, 
of 
Insoluble 
Residue. 
Per cent. 
Soluble 
in 
Acid. 
Weight of 
Si0 2 in 
Insoluble 
Residue 
(grammes). 
Per cent, 
of Si0 2 
in 
Sample. 
Per cent, 
of 
Si0 2 in 
Insoluble 
Residue. 
a 
b 
c=100— 
a 
100 -c 
d 
» ! 
11 ! 
s j 
/=100 5 
31 
1-4796 
0-8836 
59*72 
40-28 
0-6456 
43-64 
73-06 
32 
1-8465 
1-0952 
59-31 
40-69 
0-8071 
43-71 
73-69 
35 
1-1713 
04136 
35*31 
64-69 
0*3213 
27-43 
78-08 
36 
0-8916 
0-5896 
66-13 
33-87 
0-3772 
42-31 
63-98 
39 
1-1890 
0-6561 
55-18 
44-82 
0-5276 
44-37 
80*41 
41 
1-7195 
0-9598 
55-81 
44-19 
0-7337 
33-89 
76-44 
43 
1-9403 
1 -0937 
56*37 
43-63 
0-7219 
32-41 
66-00 
45 
1-3528 
0-5774 
42-68 
57-32 
0-4433 
32-77 
76-77 
46 
1-5053 
0-5895 
39-16 
60-84 
0-4715 
31-32 
79-98 
64 
1-3351 
0-3755 
28-13 
71-87 
0-2966 
22-21 
78-98 
65 
1-4602 
0-4244 
29-06 
70-94 
0-2160 
14-79 
50-89 
86 
1-7149 
0-8339 
48-63 
51-37 
0-5851 
34-12 
70-16 
87 
1-4539 
0-6300 
43-23 
56-77 
0-5349 
36-79 
85-10 
88 
1-5478 
0-7622 
49-25 
50-75 
0-5820 
37-60 
76-36 
89 
1-6682 
0-8015 
48-04 
51-96 
0-6300 
37-68 
78-60 
Table Va. Estimation of Iron and Alumina . — The hydrochloric 
acid solution (the filtrate from the insoluble residue) was peroxidised 
with potassium chlorate, and ammonia was added till the precipitate 
locally formed was very slow in dissolving. Acetate of ammonium 
