BEHAVIOR OF STRUCTURAL MEMBERS AND MATERIALS. 73 
are not fireproof, and a very hot fire will invariably destroy them, 
notwithstanding the fact that they are made of noncombustible 
material. I had rather expected to find that some damage had been 
done by the earthquake to floors made of hollow tiles or brick arches. 
That no such damage occurred was a matter of some surprise, and 
indicates that the vertical component of the undulation was not very 
great. It is probable that the earthquake caused some cracks to 
appear in the floors, but I did not see any which could with certainty 
be ascribed to this cause. It was also a matter of some surprise that 
some of the partitions were not shaken down by the earthquake, con- 
sidering the ease with which the fire destroyed them. 
So far as fire damage was concerned, the floor systems in San Fran- 
cisco stood better than any other portion of the fireproof buildings, 
although they did not stand very well, at that. The lower webs 
came off from the hollow-tile floor arches in the same way that they 
did at Baltimore, but to a very much greater extent. The cinder- 
concrete floor slabs in many buildings were protected for a time by 
the furred ceilings previously described. Where the ceilings failed 
at an early stage, or where there had been no such ceilings, the dam- 
age to the concrete floor slabs was very apparent. The concrete was 
dehydrated to a certain extent on its lower surface, and in many of 
the slabs the reenforcement had become so hot that there was a per- 
manent deflection of greater or less extent, accompanied by cracks on 
the lower side in the middle of the span. 
Just how much damage was done by the fire to cinder-concrete slabs 
was a little difficult to determine, for the reason that most of the cin- 
der concrete used in San Francisco was evidently a very inferior 
article in the first place. There was no doubt in my mind, however, 
that the concrete near surfaces which had been exposed to the fire 
showed deterioration, as compared with that which had not been ex- 
posed to the fire, although it was all so poor that there was not much 
room for difference in quality. I saw reenforced-concrete floor slabs, 
some of cinders and some of stone, which were on the point of col- 
lapse from heat alone, although they had not quite let go. 
I also saw a number of terra-cotta floor arches which had totally 
collapsed. Some of these showed evidence of damage by masses fall- 
ing from above, but in others the collapse seemed to have been due to 
heat alone. 
Girder and beam protection was a little more efficient than the 
column coverings, but it was not adequate. Its weakness was not 
fully developed, because, in many places where the necessary heat 
existed, the columns failed first and let down the floors, so that it 
was not possible to say how much of the damage to the floor members 
was due to heat alone. In a general way, however, it may be said 
that girder coverings of metal lath and plaster were wholly inade- 
