88 THE SAN FRANCISCO EARTHQUAKE AND FIRE. 
quality and the arches were very heavy. Many of the floor beams 
were 24 inches deep, and that was consequently the depth of concrete 
at the haunches. The thickness at the crown seems to have been not 
less than 5 or 6 inches, and the span between floor beams was not 
more than 6 or 7 feet. A concrete arch of such dimensions and such 
span, even though it had been made of very poor concrete, should 
have stood perfectly well had it been depending on its own power of 
resistance alone. In a number of places where the floor did not col- 
lapse the effect of heat on the exposed lower flanges of the 24-inch 
beams was sufficient to produce a deflection of (> or 7 inches on a span 
of 25 or 30 feet. This result indicates clearly the necessity of pro- 
tecting the exposed flanges of all beams. 
PL XXVI, Z?, shows some unconsumed papers about the base 
of the cast-iron column. These papers came from a vault which 
opened into this room and the contents of which were charred, 
but not destroyed; all the combustible contents of the room proper 
were destroyed. The dark splotches on the wall in the background 
are due to spalling of the brickwork at the surface under the influ- 
ence of the fire. This phenomenon was noticed in a number of places 
in San Francisco, just as it was in Baltimore; but as a rule the spall- 
ing did not penetrate to a greater depth than half an inch, and the 
wall itself was practically as good as before. In the fire at San Fran- 
cisco, as in every oilier large fire, the right kind of brickwork proved 
to be more resistant than any other ma-terial. 
A good deal of the plaster on the interior walls in the city hall 
was on wooden furring studs and wooden laths. Why this kind of 
work should have been done is beyond comprehension. Many of the 
corridors would have suffered practically no damage but for this one 
circumstance. As the fire burned out the wooden trim of openings 
between the corridors and the rooms it gained access to the wooden 
furring and burned it out behind the plaster, thereby bringing most 
of the plaster down. There were, however, many square yards still 
standing, although the wooden furring studs and laths had been 
burned out behind. There would appear to have been no reason for 
furring these interior walls; the plaster could just as well have been 
applied to the brickwork itself. As a matter of fact, in many parts 
of the building it was so applied, though in other parts the walls 
were furred with metal lathing and studs. Why a uniform treat- 
ment was not adopted is not apparent. 
The halls of the building were generally floored with marble tile. 
Even where the heat had apparently not been very intense these tile 
floors expanded and came up, and the marble was rendered chalky, 
while the color was completely ruined. 
In this building a number of girders or lintels rested upon stone 
templates, which were exposed at the face of the wall. All such 
