8o Selections from Huxley 



perience tends to show that oyster-shells are formed by 

 the agency of oysters, and in no other way. And if there 

 were no better reasons, we should be justified, on like 

 grounds, in believing that Globigerina is not the product 

 5 of anything but vital activity. 



Happily, however, better evidence in proof of the or- 

 ganic nature of the Globigerina than that of analogy 

 is forthcoming. It so happens that calcareous skeletons, 

 exactly similar to the Globigerina of the chalk, are being 



10 formed, at the present moment, by minute living creatures, 



which flourish in multitudes, literally more numerous than 



the sands of the sea-shore, over a large extent of that part 



of the earth's surface which is covered by the ocean. 



The history of the discovery of these living Globi- 



15 gerince, and of the part which they play in rock building, 

 is singular enough. It is a discovery which, like others 

 of no less scientific importance, has arisen, incidentally, out 

 of work devoted to very different and exceedingly prac- 

 tical interests. 



20 When men first took to the sea, they speedily learned 

 to look out for shoals and rocks; and the more the 

 burthen of their ships increased, the more imperatively 

 necessary it became for sailors to ascertain with precision 

 the depth of the waters they traversed. Out of this 



25 necessity grew the use of the lead and sounding line ; and, 

 ultimately, marine-surveying, which is the recording of 

 the form of coasts and of the depth of the sea, as ascer- 

 tained by the sounding-lead, upon charts. 



At the same time, it became desirable to ascertain 



30 and to indicate the nature of the sea-bottom, since this 

 circumstance greatly affects its goodness as holding ground 

 for anchors. Some ingenious tar, whose name deserves 

 a better fate than the oblivion into which it has fallen, 

 attained this object by "arming" the bottom of the lead 



