278 Dr. Deane’s Illustrations 
Several obstacles concurred to create suspicion: the relative 
age of the rock, the high point of perfection which the im- 
pressions indicated, the anomalous size of many of the creatures, 
and, above all, the impossibility of seeing original specimens. 
It was contended that they might have been produced under 
adventitious circumstances, or be assigned to huge biped 
reptiles, inasmuch as quadrupedal monsters existed in this 
remote era, which was emphatically one of colossal life. But 
these evasive objections could not resist the force of facts, and 
were successively overthrown. It seems incredible that there 
should be any pause in acknowledging the unavoidable origin 
of the impressions. It might as well be denied that recent 
imprints upon snow were made by existing animals. From 
the laminated structure of the rock, it had, for a long time; 
been used in various domestic ways; it had been made the 
object of scientific examination; yet, with every favorable op- 
portunity for discovery, it was not finally made until 1839, 
and then by accident. But it is unnecessary now to narrate 
particulars. 
In the demonstration of these fossils, we must apply the 
laws of comparison ; or, in laying down the proposition that 
they are referable to birds, their relations to existing types must 
appear. Pl. XXII. f. 4, represents the osseous distal extremity 
and phalanges of the Heron (Ardea cinerea) left foot. Count- 
ing the ranks in each individual toe, the inner one has "^ 
the middle three, and the outer four (excluding the posterior 
toe.) Now this is the method in existing tridactylous birds, 
and is the basis of analogy. When we examine the foot, oT 
trace its impression upon yielding snow or mud, the number 
and order of the lobate swellings corresponds to the divi- 
sions shown by the engraving. The insertion of the nails i5 
identical in the living and extinct species. If it can be further 
proved that the number of feet and the order of progression 
e rresponds, we then. have irrefragable proof of the kindred 
affinities of extinct and existing races. These conditions d 
- 
"exist. The faultless impressions, represented °Y 
