CHAP. X.] CONTINUITY OF THE CHALK. 507 
Of water at various depths beneath the surface, fifty-nine 
analyses were made. Those in the first cruise, twenty-six 
in number, were chiefly from bottom-water at depths from 
25 to 1,476 fathoms. In the second cruise the twenty-one 
analyses chiefly belonged to two series,—the first of samples 
taken at intervals of 250 fathoms, from 2,090 to 250 fathoms 
inclusive; and the second of samples taken at intervals 
of fifty fathoms from 862 to 400 fathoms inclusive. In the 
third cruise twelve analyses were made,—eight of bottom-water, 
of which one-half were in the “cold area,’ and four at inter- 
mediate depths. 
The general average of the fifty-nine analyses of water taken 
helow the surface gives :— 
Percentage. Proportion. 
Oxygen. . . . = 207568 100 
Nitrogen . . . . 52240 254 
Carbonic acid. . : 27-192 132 
100°000 
It will be seen from this that while the quantity of nitrogen 
is only 1:97 per cent. less than in surface-water, the quantity of 
oxygen is diminished by 448 per cent., and the quantity of 
carbonic acid increased by 6°45 per cent. ‘This difference is 
greater if bottom-waters only are compared with surface-waters. 
a 
30 Surface. | 24 Intermediate. | 35 Bottom. | 
Per ceut. |Proportion. Per cent. Proportion.| Per cent. Propor- | 
Oxygen . . «| 25°05 | 100 | 22°03 | 100 | 19°53 | 100 
Nitrogen. . . 54°21 216 | 51-82 | 235 | 52°60 | 261 
Carbonic acid . | 20°74 83 26°15 | 119 27°87 143 
| 100-00 “100°00 100-00 
The two series of analyses, before referred to, performed 
during the second cruise upon intermediate waters at successive 
depths over the same spot, both show a regular increase of the 
