410 
all been carefully examined and minutely described by the 
persons to whose researches we are indebted for their dis- 
covery. 
They were all found in the same division of the secondary 
strata, which lies in the middle region of that large and widely 
extended series of sandstones and conglomerates, limestones 
and marls, which English geologists have usually designated 
by the common appellation of the new red sandstone group, 
including all the strata that are interposed between the Coal 
formation and the Lias. No foot-prints are recorded as 
having been obtained lower in the series ; and, until lately, 
it was believed that no animals breathing by lungs existed 
during the formation of the Coal measures. 
Before I proceed to mention the localities where I have 
found fossil foot-prints in coal strata, and to describe the 
appearance of the impressions, excuse me if I make two 
short quotations, for the purpose of showing the importance 
of these foot-prints. 
Professor Phillips, in his Treatise, p. 118, has mentioned 
with approbation a speculation of M. Bronguiart, that pro- 
bably during the formation of the coal-beds the atmosphere 
contained an unusual dose of carbonic acid gas, which he 
supposes requisite for the growth of such vast forests as 
must then have encumbered the limited surface of the land. 
He admits that such an atmosphere would certainly be detri- 
mental to the life of animals breathing by lungs ; but asks, 
" what proof have we of the globe being then tenanted by 
TERRESTRIAL animals f and adds, " Now, surely, it is 
worthy of attention, that after the coal was deposited, 
reptile life began to be manifested, and finally to predomi- 
nate." 
This hypothesis has been elegantly expounded also by Mr. 
Burnet, Professor of Botany, in King's College, London, as 
follows: — The office of ferns, and the other plants of the 
