READING RIDDLES OF THE ROCKS 115 
ries, but much depends on whether the fossil 
lies in comparatively loose shale or is imbedded 
in the solid rock, whether the strata are level 
or dip downward into the hillside. If, unfort- 
unately, this last is the case, it necessitates a 
careful shoring up of the excavation with props 
of cotton-wood or such boards as may have 
been brought along to box specimens, or it may 
even be necessary to run a short tunnel in or- 
der to get at some coveted bone. Should the 
specimen lie in shale, as is the case with most 
of the large reptiles that have been collected, 
much of that work may be done with pick and 
shovel; but if it is desirable or necessary to 
work in firm rock, drills and hammers, wedges, 
even powder, may be needed to rend from Nat- 
ure her long-kept secrets. In any event, a 
detailed plan is made of the excavation, and 
each piece of bone or section of rock duly re- 
corded therein by letter and number, so that 
later on the relation of the parts to one an- 
other may be known, or the various sections as- 
sembled in the work-room exactly as they lay 
in the quarry. Bones which lie in loose rock 
are often, one might say usually, more or less 
