154 
THE VOYAGE OF H.M.S. CHALLENGER. 
same locality jus on tlic 18th of February; the dredge again brought up more of the 
black Coral fragments coated with manganese. In 2300 and 2400 fathoms farther south 
a Globigcriua (Ooze with 64 and 58 per cent, of carbonate of lime was obtained ; there 
were no Pteropod or Heteropod shells in these deposits. The mineral particles were 
chreflj’ volcanic, with a mean dijimeter of 0'07 mm., but here also small rounded grains 
of qujirtz were found, which, with similar particles observed in the sounding from 2675 
fathoms to the north-west of Madeira, appear to be wind-borne fragments, carried 
from Africa by the Harmattan winds. Soundings in 2075 and 1795 fathoms gave a 
Globigerina Ooze with 60 and 57 per cent, of carbonate of lime. About 1 per cent, of 
these deposits was made up of Radiolaria and fragments of other siliceous organisms, 
the remainder being composed of volcanic minerals, a few grains of quartz, and clayey 
matter. 
The mineral particles throughout' this section were of volcanic origin, decreasing in 
size and quantity after leaving Madeira, and increasing in both respects as St. Vincent 
was approached. 
Off Cape Verde Islands. — The deposits in the vicinity of the Cape Verde Islands (see 
Chart 11) from 200 down to a depth of 1150 fathoms were Volcanic Muds, with a varying 
]>roportion of carbonate of lime, from 8 to 56 per cent., in which Pteropod and Heteropod 
shells were abundant. In the harbour of St. Vincent the deposit in depths of 7 to 
50 fathoms was a Calcareous Sand, with 87 to 94 per cent, of carbonate of lime, chiefly 
made up of Foraminifera shells and calcareous Algae. In some places the shells of 
Amphistexjina lessonii made up fully two-thirds of the whole deposit ; Polystomella, 
Discorhina, and Orhicidina were also abundant. The mineral particles in these deposits 
decreased in size and abundance with distance from the land. 
Cape Verdes to St. Pauls Rocks. — The line of this section runs south-east from St. 
Vincent towards Cape Palmas on the Guinea coast ; thereafter it bends round and runs 
nearly due west to St. Paul’s Rocks (see Chart 12). 
Tlie deposits at the two depths, 2575 and 2500 fathoms, near the African coast, con- 
tained respectively 30 and 6 per cent, of carbonate of lime, the small percentage in the 
latter being due to the abundance of continental debris, but at all the other stations the 
de]>osit wa.s a Globigerina Ooze with over 50 per cent. ; at 1850 fathoms in Mid- Atlantic 
the amount reached 90 per cent. In all the deposits the carbonate of lime consisted 
chiefly of pehigic Foraminifera and Coccoliths, with a few fragments of Echinoderms and 
other organisms ; Rhabdoliths jilso were present in considerable quantity except at 
Stations 101 and 102. An analysis of the mud from the dredge at Station 102 (2450 
fathoms) gave 83 per cent, of carbonate of lime, while the specimen from the sounding 
tube gave only 66 ’27 per cent. A careful examination of a large quantity of this deposit 
showed tlijit nearly the whole of the carbonate of lime present came from the dead shells of 
surface organisms. It is estimated that of the 83 per cent, of carbonate of lime, 75 per 
