BEHAVIOR OF INDIVIDUAL STRUCTURES. 87 
a temporary platform covered with bunting, which had evidently 
been used on the occasion of some meeting, was practically undam-' 
aged, except for the material which had been precipitated upon it. 
The main structure of the building itself, to the southwest of the 
tower, as shown in the foreground and to the left in PI. XXXI,. was 
badly racked by the earthquake. There was very little damage from 
fire in this part of the building. Either the vibration due to the 
earthquake or the impact of falling material removed a good deal 
of plaster from the walls in the part of the building immediately 
behind the two columns that are still standing, with the portion of 
the entablature that they supported. A large part of the building 
was entirely gutted by the fire, so that, in my judgment, it would cost 
about as much to remove the debris and restore this building as it 
cost to put up the building originally. 
In the northwest corner of the building there was a pavilion which 
had a row of free columns still standing. In the middle of the west 
front of the building there had been a pavilion with a similar row 
of columns, all of which, with their entablatures, were precipitated 
into the street. These columns were composed of drums of cast iron 
with annular rebates which enabled them to be securely seated and 
centered on each other. The interior of each shaft was filled with 
broken-brick concrete of a very good quality. The columns were 
very heavy and massive, and it must have required an extremely 
severe shock to detach their entablatures from the rest of the build- 
ing and then to throw the whole mass into the street. 
The effect of the fire on the interior of the city hall was very inter- 
esting. Some parts of the ceiling remained in place sufficiently long 
to protect the corrugated-iron arches from damage; in fact, some of 
the ceiling did not come down at all. Such a case is presented in PI. 
XXVI, B, which shows the incipient failure of a naked cast-iron 
column and a ceiling that was evidently on the point of coming down. 
Where the fire was intense it brought the ceiling down in time 
to permit serious damage to the corrugated-iron arches and their con- 
crete filling. Wherever these arches were exposed directly to much 
heat the first effect was to cause them to expand and rise at the 
crown, which generally resulted in shattering the concrete Idling im- 
mediately over the crown. Further application of the heal caused 
the corrugated-iron arch to soften and come down altogether. When 
it did, the concrete followed it. the portion at the crown being too 
much shattered to act as a key. In this way the total collapse of 
large areas of floor construction in the city hall was brought about. 
The concrete arch would have stood better alone than it did with cor- 
rugated iron underneath it; indeed, it is doubtful whether any of the 
concrete arches would have collapsed but for the damage done by the 
expansion of the corrugated iron. The concrete was of a very fair 
