na which had taken place
on this spot during the human period. Even as late as three hundred
and ninety years after the foundation of Rome, a chasm opened in the
Forum, and emitted flames and pestilential vapours. An oracle declared
that this chasm would not close until what constituted the glory of
Rome should be cast into it. Marcus Curtius asked if anything in Rome
was more precious than arms and valour; and arraying himself in his
armour, and mounting on a horse splendidly equipped, he leapt in the
presence of the Roman people into the abyss, when it instantly closed
for ever. We thus see that the geology of the Roman plain throws no
inconsiderable light upon the early history and traditions of the
Eternal City, and brings within the cycle of natural phenomena what
were long supposed to be purely fabulous incidents, the inventions of
a poetic imagination. I have dwelt upon these geological incidents so
fully, because nowhere does one realise the striking contrast between
the shortness of man's existence on earth, as in places like the Roman
plain, where the traces of cosmical energy have been greatest and most
enduring.

The volcanic origin of the Roman Forum suggests the curious idea of
the intimate connection of some of the greatest events of history with
volcanic centres. Where the strife of nature has been fiercest, there
by a strange coincidence the storm of human passion has been greatest.
The geological history of a region is most frequently typical of its
human history. We can predicate of a scene where the cosmical
disturbance has been great,--where fire and flood have contended for
the mastery, leaving the effects of their strife in deepening valleys
and ascending hills,--that there man has had a strangely varied and
eventful career. The strongholds and citadels of the earth, where the
great battles of freedom and civilisation have been fought, were all
untold ages previously the centres of violent plutonic disturbances.
Edinburgh Castle, enthroned on its trap-rock, once the centre of a
volcano, is associated with the most stirring and important events in
the history of Scotland; Stirling Castle rises on its trap-rock
erupted by volcanic action above a vast plain, across which a hundred
battles have swept; Dumbarton Castle, crowning its trappean
promontory, has represented in its civil history the protracted
periods of earthquake and eruption concerned in the formation of its
site; while standing in solit