ANNIVERSARY ADDRESS. 19 



also sink to the bottom, but are not found much south of Prince 

 Edward Island, north to the west of Faroe. 



The " Grlobigerina ooze " is limited to certain depths — about 

 2,250 fathoms. Below 2,500 fathoms the calcareous formation 

 passes to a red clay, which is a silicate of the red oxide of iron 

 and alumina. The shells in the ooze gradually lose their distinct- 

 ness, become brownish, and more and more mixed with red powder 

 till the lime disappears. Between the two substances comes in 

 the "grey ooze," which has an intermediate character. The 

 proportion of the two extreme deposits is 1,900 miles of red clay 

 to 720 miles of Globigerina ooze. The mean maximum depth of 

 the latter is 2,250 fathoms, that of grey ooze 2,400, of the red 

 clay 2,700 fathoms. Wherever the depth increases from about 

 2,200 to 2,600 fathoms, the modern chalk formation of the 

 Atlantic and of other oceans passes into red clay. 



"What is the origin of this red clay ? Though pelagic mollusca 

 swarm in the mid- Atlantic, their shells are found in the Globi- 

 gerina ooze, but never in the red clay ; and the facts observed 

 show that they probably have been removed from the latter in 

 some way after death. The conclusion come to is that the " red 

 clay " is not anything from without, but that the lime, which 

 forms 98 per cent, of the Globigerina ooze, is removed from it, 

 and the red clay is considered to be the " essentially insoluble 

 residue " — the ash, as it were, of the calcareous organisms of the 

 ooze after the calcareous matter has been removed. A mixture 

 of the shells Tor ming the ooze from near St. Thomas's Island was 

 submitted to the action of weak acid, and after the lime was 

 removed there was left about 1 per cent, of reddish mud, consist- 

 ing of alumina, silica, and the red oxide of iron. This experi- 

 ment has often been repeated with the same result. 



On the 13th March the trawl brought up a large quantity of 

 nodules of the peroxide of manganese, and they appear generally 

 in the "red clay," never in the " ooze" ; but no sooner had the 

 removal of the carbonate of lime commenced than small black 

 grains became apparent and represented the nodules common in 

 the red clay when the manganese is in very considerable propor- 



