MACKIE — ROCKS AND THEIR TEACHINGS. 99 
thickness as the depression or elevation of the old continent on which 
they rest went slowly on — thus : 
LtGS. 12. r.iGN. 13. 
"When these sediments were elevated into dry land, and, as they rose out 
of the waves, being subjected to the denudation or slicing-off of their 
upper extremities, they would offer the conditions represented below— ^ 
thus : 
LiGN. 14.— Strata thinning out on an olil nueven soa-licd. 
a II 
s 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
c 
r 
Lion. Strata thickening downwards on an nneven sea-hcd. 
Suppose the beds to be of equal thickness ; then we should not always 
get a true idea from tlicir outcrops of the nuniber of the beds 
beneath the point (Lign. IG), and consequently we might be as far 
L 2 
I 
