ANNIVERSARY ADDRESS OF THE PRESIDENT. xli 
as we approach the site of London by a greater depth of sea, whereby 
the shallow-water and littoral fauna of the Bognor deposits had its 
character altered by new forms, such as the Nautilus, Peutacrinites 
and other deeper sea animals, the remains of which abound in the 
London clay near London. 
When we regard the mode in which organic remains may become 
mingled with the mineral matter in which they may be found, it is 
very important to consider the character of the latter immediately in 
contact with the former. Physical conditions can so readily have 
changed during the accumulation of a series of beds, that greater or 
less portions of subaqueous areas upon which certain kinds of animals 
may exist under the circumstances best fitted for them, may become 
so modified or even wholly changed as respects such conditions, that 
the animals become scarce or disappear; and yet a return of the 
needful conditions may enable germs borne from some locality where 
the physical circumstances have remained suitable to the existence of 
their parents, to establish themselves, and the mineral accumulations 
of the locality be again charged with the harder remains of this species 
as heretofore. Mud, under the needful conditions, can be accumulated 
in waters of very varied depths, and gravels which could, under ordi- 
nary circumstances, be only formed or accumulated in shallowsituations 
or beaches, might be depressed, and not be covered by any other 
deposits, until the remains of animals, which could then be entombed, 
no longer belonged to the class of those which lived in shallow water. 
Indeed it might so happen that some of the animals inhabiting the 
bottom, after the depression of the gravel, might penetrate among 
the pebbles, particularly if large, so that m after geological times the 
upper portions of such a gravel may contain the remains of animals 
which did not live in the situations where the gravel was either formed 
oraccumulated. Touching the chances of such changes of conditions, 
it may be observed, that there is no want among the coasts of the 
world of irregular fringes of gravel and shingle along lines of deep 
sea-coasts, where, if depressions of the land, relatively to the sea, did 
take place, such shingle accumulations might descend into seas to 
which little sand, and even little mud, could be for a long period 
borne, though no doubt from changes of physical conditions, such as 
the study of geology teaches us have often taken place, any such 
mass of shingles may finally become well covered by arenaceous and 
argillaceous accumulations. 
That the mass of coal-bearmg beds of the paleeozoic period were ac- 
cumulated in shallow water, a gradual subsidence of the land taking 
place, the coal-beds themselves being the remains of plants which have 
grown in the atmosphere and upon the subjacent deposits on which 
they repose, when the accumulations became such as to reach to the 
surface, has now become a common opinion. Still every additional 
good evidence on this point is not without its value. Mr. Richard 
Brown, in his description of an upright stem above the Sydney main 
coal, in the island of Cape Breton, wherein he concludes that Stigma- 
ria roots are attached to a stem of Lepidodendron, shows that this 
plant grew where it is now found, its roots spreading, out above the 
