JO 



BIOLOGICAL LECTURES. 



sand, mud, or other sediment upon it will, if sufficient in quan- 

 tity, bury it completely and prevent its being scattered, and 

 thus fossilize it as a skeleton. If, on the other hand, the car- 

 cass is only lightly weighted by silt, it will rise to the surface, 

 when the gases engendered by decomposition begin to inflate 

 and distend the abdominal walls. Floating thus, being pulled 

 about and partially eaten by carnivorous fishes and reptiles, it 

 will drop a limb here, a jaw there, a few vertebrae in another 

 place, until the fragments are scattered over a wide area of the 

 lake bottom. 



In any case, when a specimen is taken at all, the cardinal 

 rule of collecting is to take the whole of it, not allowing the 

 smallest recoverable fragment to escape. It is surprising to 

 see what great importance tiny fragments may assume, when 

 the work of piecing together the broken bones is undertaken ; 

 the presence or absence of such a fragment may determine 

 success or failure in this patchwork. The most unpromising 

 heap of fragments may often be converted by skill and patience 

 into beautiful specimens, not, as the uninitiated sometimes sup- 

 pose, by the liberal employment of the imagination and plaster 

 of Paris {though this has been done), but by the actual fitting 

 together of the broken pieces of bone. The careful collector 

 knows all this, and spares neither time nor pains to find all the 

 fragments which have been weathered out, even washing and 

 sifting the soil, when necessary for his purpose. 



When the fossil has not suffered from the weather, but 

 remains intact, the manner in which it can best be taken up 

 will depend upon a variety of circumstances, and especially 

 upon the firmness of the rock and of the bones. If the 

 rock is fairly hard, not traversed by many or irregular joints 

 or cracks, the best method is carefully to expose enough of the 

 specimen to determine its size, and then with pick, or hammer 

 and chisel, cut a deep groove in the rock all around the fossil, 

 making sure that the groove is deep enough to clear the bones, 

 then by driving wedges beneath the block thus isolated, raise it 

 in one mass. If the fossil is too large to be handled in one 

 piece, it may be taken up in several blocks and packed for 

 transportation. 



