THE CHALK 43 



On the shore near Shanklin you will often see streaks of 

 what look like tiny bits of broken shell washed into 

 depressions in the sand. These, however, often consist 

 almost entirely of complete microscopic shells, some of 

 them of great beauty. The creature that lives in one 

 of these shells is only like a drop of formless jelly, and yet 

 around itself it forms a complex shell of surprising beauty. 

 The shells are pierced with a number of holes, hence their 

 name (fr. Lat. foramen, a hole, and ferre, to bear). 

 Through these holes the animal puts out a number of 

 feelers like threads of jelly, and in these entangles particles 

 of food, and draws them into itself. Now, do we anywhere 

 to-day find these tiny shells in such masses as to build 

 up rocks ? We do. The sounding apparatus, with which 

 we measure the depths of the sea, is so constructed as to 

 bring up a specimen of the sea bottom. This has been 

 used in the Atlantic, and it is found that the really deep 

 sea bottom, too far out for rivers and currents to bring 

 sand and mud from the land, is covered with a white mud 

 or ooze. And the microscope shows this to be made up 

 of an unnumerable multitude of the tiny shells of forami- 

 nifera. As the little creatures die in the sea, their shells 

 accumulate on the bottom, and in time will be pressed 

 into a hard mass like chalk, the whole being cemented 

 together by carbonate of lime, in the way we explained 

 in describing the making of limestones. So we find chalk 

 still forming at the present day. But what ages it must 

 take to form strata of solid rock of such tiny shells ! And 

 what a vast period of time it must have required to build 

 up our chalk cliffs and downs, composed in large part of 

 tiny microscopic shells ! With the foraminifera the 

 microscope shows in the chalk a multitude of crushed 

 fragments, largely the prisms which compose bivalve 

 shells, flakes of shells of Terebratula and Rhynchonella, 

 and minute fragments of corals and Bryozoa. Scattered 

 in the chalk we shall also find larger shells and other 



