THE SEA FLOOR 165 



gradient varying from i in 660 to i in 300, to a 

 depth of 100 fathoms ; but after that, at a distance 

 75 35 rniles from shore, it makes an exceedingly 

 steep descent — the gradient being about i in 19 — 

 down to 1000 fathoms, the bottom still being mud 

 derived from the land. In fact, if the water could 

 suddenly be run out of this sea, we should find the 

 Malabar coast fringed by a shelf of mud from 50 

 to 100 miles wide, and having a steep fall of more 

 than 5000 feet. On the Laccadive side the bottom 

 is utterly different : here from a broken and uneven 

 bed of calcareous ooze the reefs and islands rise 

 suddenly up, as a chain of mountain peaks rise out 

 of an undulating plain. The calcareous ooze is made 

 up partly by the waste of the coral-reefs themselves 

 and partly by the shells of Foraminifera that fall 

 from near the surface of the sea. Besides the mud 

 and calcareous ooze already mentioned, we find in 

 places green sand," which largely consists of the 

 shells of Foraminifera — or casts of them — impreg- 

 nated with glauconite. As to the depth of the 

 Laccadive Sea, the deepest sounding yet taken, a 

 little south of lat. 10° N., is about 1500 fathoms. 

 Its surface temperature ranges between 80° and 90° 

 Fahr., according to the time of year ; but its tempera- 

 ture at 1300 fathoms is only 35° Fahr., at about 

 1000 fathoms is only about 38° Fahr., and even at 

 300 fathoms is not higher than 51° Fahr., which is 



