82 EXIINCT: MONSTERS. 
to south, in the States of Massachusetts and Connecticut. After 
visiting several of these places, I entertained no doubt that the 
sand and mud were deposited on an area which was slowly sub- 
siding all the while, so that at some points a thickness of more 
than a thousand feet of superimposed strata had accumulated in 
very shallow water, the footprints being repeated at various intervals 
on the surface of the mud throughout the entire series of super- 
imposed beds.” When Sir Charles Lyell first examined this 
region in 1842, Professor Hitchcock had already seen two thousand 
impressions of feet! 
It is not difficult to imagine the conditions under which such 
impressions may have been preserved, for at the present day 
there are to be seen, on some shores, illustrations of similar opera- 
tions. Dr. Gould, of Boston, U.S., was the first to call the 
attention of naturalists to a very instructive example of such 
processes on the shores of the Bay of Fundy, where the tide is 
said to rise in some places seventy feet high, Here we have 
a very perfect surface for receiving and retaining impressions. 
Vast are the numbers of wading and sea-birds that course to and 
fro over the extensive tract of plastic red surface left dry by the 
far retreat of the tide in the Bay of Fundy. During the period 
that elapses between one spring tide and the next, the highest 
part of the tidal deposit is exposed long enough to receive and 
retain many impressions ; even during the hours ef hot sunshine, 
to which, in the summer months, this so-trodden tract is left 
exposed, the layer last deposited becomes baked hard and dry, 
and before the returning tidal wave has power to break up the 
preceding one, the impressions left on that stratum have received 
a deposit. A cast is thus taken of the mould previously made, 
and each succeeding tide brings another layer of deposit. We 
can easily imagine that in succeeding ages the petrifying influences 
will consolidate the sandy layers into a fossil rock. Such a rock 
would split in such a way, along its natural layers of formation, as 
to show the old moulds on one surface, and the casts on the other. 
