196 Proceedings of the Royal Physical Society, 
of the British systems. To abide by these systems were to 
set up our petty archipelago as the type of the wider world, 
and to retard the progress of geology ; and we may rely on 
it that the time is fast drawing near when we must both 
modify and intercalate — modify what we now consider sys- 
tems, and intercalate others to which there is no equivalent 
in these islands. It is true that, under the present " sy sto- 
mal arrangements," geology has made most excellent pro- 
gress, and these on that account should not be lightly aban- 
doned ; but to be ever forcing unnatural co-ordinations is 
obstructive alike to truth and the labours of the distant 
observer. As the old arrangements of Lehman and Werner 
gave way to the wider knowledge of the present day, so 
we may naturally expect the arrangements of the present 
to be superseded by the more exact information of future 
observers. 
Contemporaneity. — And this difficulty of co-ordination 
brings us, in the fifth place, to remark on the very difficult 
but most important question of contemporaneity ^ or contem- 
poraneous formations. Hitherto the general idea has been 
that identity of genera and species in any set of strata, 
however widely separated, was proof of contemporaneity of 
deposit. Founding on this notion, a thousand facts in geo- 
logy became inexplicable ; but believing that species and 
genera in time past had their centres and areas of distribu- 
tion just as they have at the present day, and that under 
the oscillations of sea and land they may have taken ages 
to travel from one hemisphere to another, the difficulties 
vanish, and we require to call in no abnormal conditions of 
universal sameness of life, sameness of climate, changes 
in the earth's axis of rotation, or such like causes, at total 
variance with all that we know of the present ordainings 
of the universe. Identity of species, therefore, unless in 
limited areas, instead of proving contemporaneity of de- 
posit, would go to prove the reverse, and would merely 
show that the areas in which they are now found fossil 
had at one time or other the means of transference placed 
between them. From this view, then, it by no means fol- 
lows that the palaeozoic coal-fields of America were con tern- 
