To remedy this defect, the
architect caused _spherical pots_ to be baked; of these each formed of
itself an arch sufficiently powerful to sustain its share of the
incumbent weight, and the whole was rendered much less ponderous by the
innumerable vacuities.
[Illustration]
"A similiar expedient was likewise used to diminish the pressure of
their domes, by employing the scoriae of lava brought for that purpose
from the Lipari Islands. The numberless bubbles of this volcanic
substance give it the appearance of a honeycomb, and answer the same
purpose as the pots in Caracalla's Circus, so much so, that though very
hard, it is of less specific gravity than wood, and consequently floats
in water."
Before I quit the Circus of Caracalla, I must not forbear mentioning his
bust, which so perfectly resembles Hogarth's idle 'Prentice; but why
should they not be alike?
For black-guards are black-guards in every degree,
I suppose, and the people here who shew one things, always take delight
to souce an Englishman's hat upon his head, as if they thought so too.
This morning's ramble let us to see the old grotto, sacred to Numa's
famous nymph, AEgeria, not far from Rome even now. I wonder that it
should escape being built round when Rome was so extensive as to contain
the crowds which we are told were lodged in it.
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