154 TlMEHRI. 
Wherever, then, there has been the slightest crack in 
its surface, rain water gathers, and having once obtained 
a lodgment it eats away and enlarges the crack. The 
result is an eppelling surface which, instead of being like 
an asphalt pavement, is like a pavement formed of irreg- 
ularly-shaped and scattered flag-stones. But again, the 
mud-layer which overlies the eppelling being by no 
means thick, whenever this has once been indented, as 
just described, by many cracks enlarged by water, these 
cracks are soon engraved through the mud-layer down to 
the soft sandstone below ; and, when this has once 
occurred, the sandstone thus exposed, which yields to 
the action of the water even more readily than does the 
hard mud, is rapidly worked out. In this way the eppel- 
ling is made to assume the form of a number of blocks, 
often pillar-like, of sandstone, each of these blocks being 
capped and protected by a patch of the original hard 
earth, or, in other cases, of the original conglomerate. 
Now, where the original eppelling surface is unbroken, 
in which state we have compared it to an asphalt pave- 
ment, it is as entirely devoid of vegetation as such an 
artificial pavement would be. But where the surface of 
the eppelling has reached its furrowed stage, a few plants 
find lodgment, chiefly certain orchids and other such 
plants, of which the roots are of such a nature that, in 
the dry season, when the furrows are water-less, the 
whole plant shrinks into complete rest, and even in some 
cases loses its root-hold and is blown about on the 
surface of the eppelling until, when the next rains 
come, it again throws out anchor-like roots into some 
new furrow. One orchid of this wandering tendency 
is a Catasetum (C. cristatum ?) [No. 148]; another is 
