METHODS OF PALAEONTOLOGICAL INQUIRY. 69 



ground must be examined by traversing it along such lines as 

 will best expose the surface to the eye of the seeker, and some 

 of the best workmen make their preliminary examinations of 

 the ground and " locate their finds" on horseback. The ex- 

 traordinary climbing powers of the western broncho make him 

 an invaluable adjunct in the work. This bone-hunting requires 

 for its successful prosecution great keenness of vision and that 

 trained aptitude which enables the hunter to rapidly but thor- 

 oughly examine the ground, not allowing the glance merely to 

 wander over the surface, but concentrating the attention upon 

 every successive square rod. The silicified bones are harder 

 than the rock or matrix which contains them, so that the proc- 

 ess of weathering leaves them standing in relief; but, as the 

 weather is destructive to the fossils also, the longer a specimen 

 has been exposed, the more injured it is. A consequence of 

 this is that the most desirable specimens are those which are 

 the hardest to find, because least exposed. 



When a fragment of bone is seen, it may prove to be the 

 guide to a whole skeleton, and therefore no indication can be 

 neglected. If the fragment is lying loose upon the surface, it 

 must be traced to its parent ledge, remembering that it has 

 been washed downward, and a line of fragments will lead the 

 collector to the spot whence they have all been derived. More 

 favorable is the case where the visible fragment is still in place 

 and is the only portion of the specimen exposed, the rest being 

 concealed in the shelter of the rock; such concealed specimens 

 are almost always the best. When excavated, the specimen 

 may prove to be a few teeth, a limb bone, a skull, a complete 

 limb or foot, or even a whole skeleton ; of course, skeletons are 

 rare and constitute the great prizes of the collector. At first 

 sight, it may seem puzzling why a skeleton should be preserved 

 nearly or quite intact in one case, and in another only a single 

 bone should be found; to understand this we must consider 

 something of the conditions under which animals are fossilized. 



When a land mammal is drowned, the body, being somewhat 

 heavier than water, sinks to the bottom at once, though a swift 

 current may transport it for considerable distances. When it 

 finally comes to rest upon the bottom, the rapid deposition of 



