38 BULLETIN OF THE 



The mineral particles consist of fragments of ancient rocks, quartz, 

 monoclinic and triclinia felspars, magnetite, hornblende, augite, mica, 

 tourmaline, and occasionally glauconitic grains. 



In 1240 fathoms, and Lat. 38° 34' N. oflf this coast, the "Challenger" 

 dredged many rounded and angular pebbles of milky and hyaline quartz, 

 fine-grained quartzites, felspathic quartzites, mica schists, serpentine 

 rocks, and compact limestones. These fragments were not larger than 

 6 or 7 centimetres in diameter. The "Blake," in 1241 fathoms and 

 Lat. 39° 43' N., dredged similar, but much larger, fragments of the same 

 rocks, some of which were glaciated. In Lat. 41° 14' N. and in a 

 depth of 1340 fathoms, the "Challenger" again dredged similar rock 

 fragments, and one block of syenite weighing 5 cwt. These deposits 

 being all within the influence of the Labrador Current, these rocks may 

 be regarded as chiefly ice-borne. 



The carbonate of lime in these deposits consists of coccoliths and 

 coccospheres, of pelagic and other Foraminifera, and of fragments of 

 Echinoderms, Polyzoa, Ostracodes, and Mollusks. The pelagic Forami- 

 nifera shells and coccospheres are more abundant in the deeper deposits 

 far from the land than in those from shallower water near the coast. 



The siliceous remains of Diatoms, Radiolarians, and Sponges, together 

 with arenaceous Foraminifera, and glauconitic casts of calcareous Foram- 

 inifera make up sometimes 4 or 5 per cent of the deposit. 



The following are descriptions of some of the typical deposits : ^ — 



Station 305. — Lat. 41° 13' 53" N. Long. GS** 57' 25" W. Deptli, 810 fath- 

 oms. Surf. temp. 56:^°. Bot. temp. 39°. Gray mud, browu when wet, earthy, 

 plastic, dries into hard lumps. Mixed with the mud were some few piunulse of 

 Crinoids, also a few rock fragments (sandstone, diorite, and diabase) measuring 

 from 10 to 30 milUmetres in diameter. 



Carbonate of Calcium, 5.08 per cent, consists of coocoliths and coccospheres, 

 fragments of Echinoderms, and the following foraminifera : — 



^ The methods employed in the examination of these deposits are the same as those 

 adopted by Messrs. Murray and Renard for the Challenger deposits. The carbonate 

 of calcium was determined by estimating the carbonic acid, weak and cold hydro- 

 chloric acid being used for the purpose. The part insoluble in the acid is designated 

 "residue," which by washing, decantation, and microscopic in.spection is separated 

 into three parts : (a) Minerals, the contraction m. di. indicating their mean diameter 

 in millimetres ; {h) Siliceo-us Organisms, including the glauconitic casts of forami- 

 nifera and other calcareous organisms ; (c) Fine Washings, including those particles 

 which, resting in suspension, pass with the first decantation. The numbers in 

 brackets indicate the percentage of the whole deposit. 



