shape would not suffice to bring them
even so near to a horizontal line but that the most inaccurate and
unobservant eye should at once detect the inequality in their level;
and the chains themselves would probably give way before such a force
as this could be applied to them. The least diameter of the Coliseum
is nearly equal in length to the Menai bridge; and if the labor of
stretching cords over the one seems small in comparison with that of
raising the ponderous chains of the other, we may take into
consideration the weight of cloth which those cords supported, and the
increase of difficulties arising from the action of the wind on so
extensive a surface.

In boisterous weather, as we learn from Martial and other authors,
these difficulties were so great that the velum could not be spread.
When this was the case the Romans used broad hats, or a sort of
parasol, which was called _umbella_ or _umbraculum_, from _umbra_,
shade. We may add, in conclusion, that Suctonius mentions as one of
Caligula's tyrannical extravagances, that sometimes at a show of
gladiators, when the sun's heat was most intense, he would cause the
awning to be drawn back, and, at the same time, forbid any person to
leave the place.

The difficulty of the undertaking has given rise to considerable
discussion as to the means by which the Romans contrived to extend the
velum at such a height over so great a surface, and to manage it at
pleasure. Sailors were employed in the service, for the Emperor
Commodus, who piqued himself on his gladiatorial skill, and used to
fight in the arena, believing himself mocked by the servile crowd of
spectators, when once they hailed him with divine honors, gave
order for their slaughter by the sailors who were managing the veils.

[Illustration: COLISEUM OF ROME.]

Concerning the method of working them no information has been handed
down. It is evident, however, that they were supported by masts which
rose above the summit of the walls. Near the top of the outer wall of
the Coliseum there are 240 consoles, or projecting blocks of stone, in
which holes are cut to receive the ends of spars, which ran up through
holes cut in the cornice to some height above the greatest elevation
of the building. A sufficient number of firm points of support at
equal intervals was thus procured; and, this difficulty being
overcome, the next was to stretch as tight as possible the larger
ropes, upon which the whole covering dep