346 THE CAUSES OF THE XI 



in their continuity, or any very great distance 

 between the points to be compared. 



Well now, so much for the record itself, so 

 much for its imperfections, so much for the con- 

 ditions to be observed in interpreting it, and its 

 chronological indications, the moment we pass 

 beyond the limits of a vertical linear section. 



Now let us pass from the record to that which it 

 contains, from the book itself to the writing and 

 the figures on its pages. This writing and these 

 figures consist of remains of animals and plants 

 which, in the great majority of cases, have lived 

 and died in the very spot in which we now find 

 them, or at least in the immediate vicinity. You 

 must all of you be aware and I referred to the 

 fact in my last lecture that there are vast 

 numbers of creatures living at the bottom of the 

 sea. These creatures, like all others, sooner or 

 later die, and their shells and hard parts lie at 

 the bottom ; and then the fine mud which is 

 being constantly brought down by rivers and the 

 action of the wear and tear of the sea, covers 

 them over and protects them from any further 

 change or alteration ; and, of course, as in process 

 of time the mud becomes hardened and solidified, 

 the shells of these animals are preserved and 

 firmly imbedded in the limestone or sandstone 

 which is being thus formed. You may see in the 

 galleries of the Museum up stairs specimens of 

 limestones in which such fossil remains of existing 



