795 
_ With respect to the impressions having been made by birds, Mr. 
Lyell states, that until he examined the whole of the evidence he 
entertained some scepticism, notwithstanding the luminous account 
given by Prof. Hitchcock. In proof of their being the foot-prints of 
some creature walking on mud or sand, he mentions, Ist, the fact of 
Prof. Hitchcock’s having seen 2000 impressions, all, like those he had 
himself examined, indented in the upper surface of the layer, the 
casts in relief being always on the lower surface ; and 2ndly, that 
where there is a single line of impressions the marks are uniform in 
size, and nearly uniform in distance from each other, the toes in the 
successive steps turning alternately right and left. Such single lines, 
Mr. Lyell says, indicate that the animal was a biped, and the trifid 
marks resemble those which a bird leaves, there being generally a 
deviation from a straight line in any three successive prints ; and his 
attention having been called to indications of joints in the different 
toes, he afterwards clearly recognised similar markings in the recent 
steps of coots and other birds on the sands of the shores of Massa- 
chusetts. Prof. Hitchcock has shown, that the same impression ex- 
tends through several lamine, decreasing in distinctness in propor- 
tion as the layer recedes from that in which it is most strongly marked, 
or in proportion as the sediment filled up the hollows and restored 
the surface to a level; and Mr. Lyell states, that he has observed a 
great number of instances of this fact. 
He also says, that he can scarcely doubt that some of the impres- 
sions on the red sandstone of Connecticut are not referable to birds, 
but he believes that the gigantic ones described by Prof. Hitchcock 
are Ornithichnites. At Smith’s Ferry they are so numerous that 
a bed of shale many yards square is trodden into a most irregular 
and jagged surface, so that there is not a trace of a distinct footstep ; 
but on withdrawing from this area to spots where the same tracts are 
fewer, the observer, Mr. Lyell says, is forcedto admit that the effect 
in each case has been produced by this cause. 
On examining the shores on some small islands about fifteen miles 
south-east from Savannah, the author was struck with the number as 
well as the clearness of the tracks of raccoons and opossums imprinted 
in the mud during the four preceding hours, or after the tide had be- 
gun toebb. At one spot, where the raccoons had been attracted by 
the oysters, the impressions were as confused as when a flock of 
sheep has passed over a muddy road ; and in consequence of a gentle 
breeze blowing parallel to the line of cliffs composed of quartzose 
sand, the tracks had in many places already become half filled with 
blown sand, and in others were entirely obliterated ; so that if the 
coast should subside, the consolidation of this sand would afford 
casts analogous to those of Storeton Hill in Cheshire, yet the im- 
pressions had been made and filled in a few hours. 
When considering the broad question whether the fossil foot-prints 
were made by creatures walking on mud or sand after the ebbing of 
the tide, Mr. Lyell reminds his readers of the fact that in the United 
States, as in Saxony and Cheshire, the tracks in sandstone and shale 
