READING RIDDLES OF THE ROCKS 115 



ries, but much depends on whether the fossil 

 hes in comparatively loose shale or is imbedded 

 in the sohd 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 



