522 Mr. J. Murray on Oceanic Deposits examined 



red colour. These were usually very rough, and had not the delicate 

 hues of the green giauconite casts. One very remarkable exception 

 occurs : — off the Crozets there were (in 600 fathoms) many beautiful 

 casts of the carbonate-of-lime organisms of a pale straw-colour. None of 

 the giauconite grains were noticed in the same sounding or locality. 



(c) Red Mud. — It has already been stated that the deposit along the 

 east coast of South America, from Cape San Roque to Bahia, differed 

 from the deposits found along the shores of other continents and large 

 islands in being of a red colour. There can be little doubt but that this 

 red colour is due to the presence of the ochreous matter carried into the 

 Atlantic by the South- American rivers. There are reasons for thinking 

 that the red colour of some of the deep-sea clays in this region of the 

 Atlantic may have a like origin. 



The soundings near the shore and in shallow water have a deeper 

 red colour and contain larger mineral particles and fewer organic re- 

 mams than those further from land and in deeper water. The mineral 

 particles are chiefly quartz and mica. 



In all these soundings there are many pelagic and other Foraminifera, 

 Heteropod, Pteropod, larval Gasteropod, and Lamellibranch shells, Coc- 

 coliths, and Rhabdoliths. Siliceous organic remains, as of Diatoms aud 

 Padiolaria, are almost quite absent in these bottoms. In some of the 

 shallower depths a few red-coloured casts of Foraminifera were observed ; 

 but these were rare, rough, and more or less imperfect. 



The following are the depths of the soundings along this coast : — 



fins. 



fms. 



fms. 



1375 



120 



1200 



500 



32 



|700 



2050 



400 



1015 



1650 



1715 



1275 



675 



1600 



2150 



(d) Coral-Mud. — This is a deposit found in the neighbourhood of 

 coral reefs. It is characterized by a large quantity of amorphous calca- 

 reous matter, b} r the debris of coral reefs, by many large calcareous forms 

 of Foraminifera, and by broken pieces of Polyzoa, &c. All the deposits 

 about Bermuda are of this nature, extending from the edge of the reef 

 down to a depth of 2500 fathoms. At 1000 fathoms the mud assumes a 

 rose tinge ; this deepens into a red colour with greater depth and the 

 accompanying decrease of carbonate of lime and increase of clayey matter, 

 until the coral-mud merges into the red and grey clays of the surrounding 

 ocean. About Bermuda very few mineral particles were found. In some 

 of the soundings to the S.W, of the island there were some small pieces 

 of a green rock like those at St. Paul's Rocks, and probably serpentine. 

 One or two pieces of quartz, or sanidin, a piece of mica, and a small piece 

 of pumice (?) were also noticed. Dissolving away carbonate of lime in 



