XVI.] 



FORAMINIFERAL LAND. 



26; 



" telegraph plateau," has a width of more than 1000 miles, and 

 an average depth of more than 1000 fathoms. It is almost 

 uniformly covered with a wide^spread deposit of fine creamy 

 or greyish mud, generally called " ooze." When this mud 

 is dried, it hardens into a grey friable substance, which may 

 be used for writing on a board, as chalk is used. Moreover, 

 when any acid is poured upon the mud, the greater part of it 



J) 



Fig. 79- — A Globigerina bulloUes, D'Orb. ; B. Orbidina nniversa, D'Orb. ; C 

 A coccosphere ; D. A coccolith, profile and three-quarters view (after Haeckel). 



dissolves with eifervescence, just as a piece of chalk would 

 do ; and it can readily be ascertained that the ooze, like 

 chalk, consists mainly of carbonate of lime. 



This calcareous ooze, however, is not mere mineral 

 matter; for, when a little is placed under the microscope, 

 the greater part of it is seen to consist of such bodies as 

 those represented in Fig. 79 A. Each of these consists of 

 several globular chambers, one of which is smallest and one 



