74 THE SAN FRANCISCO EARTHQUAKE AND FIRE. 
quate, those of hollow tiles suffered serious damage, and those of 
solid concrete failed a little more commonly than they should, 
although they Avere the best of all. Many girders that had been 
covered with metal lath and plaster were badly warped and deflected, 
and some wholly collapsed, from the heat alone. Many beams were 
seriously deflected from the heating of exposed lower flanges. 
I was not able to learn that any serious damage had been done 
to column coverings by the earthquake. In some buildings columns 
which had not been exposed to much heat happened to be standing 
with their covering absolutely intact, while another column not far 
away in the same story of the building and evidently subjected to 
an intense heat had not only lost its covering, but had itself been 
practically destroyed by the fire. In no such case was I able to dis- 
cover any evidence of earthquake damage in the covering that was 
intact, and there was nothing to indicate that one column might 
have had its covering damaged by the earthquake, while its neighbor 
escaped. More detailed information relative to fire damage is pre- 
sented in the discussion of the individual buildings (pp. 76-108). 
The earthquake did a great deal of damage, which could easily be 
differentiated from that due to the fire. As a rule brickwork in San 
Francisco w T as laid in lime mortar or in lime mortar gaged with a 
small amount of Portland cement. Wherever such masonry was sub- 
jected to serious earthquake shocks it was very badly shattered. 
Much of it came down in the ruins, and much of that which remained 
in place was reduced to a loose pile, without any adhesion between 
the mortar and the bricks. The bricks in general were more or less 
misplaced even where they did not come down, and many of them 
were broken. Where brickwork was solidly laid up in good Portland- 
cement mortar, if the earthquake shock induced stresses sufficient to 
damage it, the damage generally appeared in the form of well-defined 
cracks, which could have been easily pointed up, so as to leave the 
wall almost as good as it Avas before. 
Well-executed stone masonry subjected to earthquake shocks 
shoAved, in many places, considerable slipping of the individual 
stones, the adhesion between the stones and the Ynortar having been 
destroyed. Here and there, AA T here the strength of the mortar ap- 
proached that of the stone, the stone itself was badly shattered and 
cracked. Where the wall ran in the direction in Avhich the undulation 
seems to have been propagated, it generally shoAved an X-shaped 
crack (PI. XXII, A), the legs of the X crossing the affected area in 
a diagonal direction. Where the masonry Avas very good these cracks 
were the only apparent damage, but Avhere it was not so good the indi- 
vidual stones, bricks, or tiles, as the case might be, had been loosened 
from their beds and broken, so that the entire mass was shattered, 
although in many places still standing. 
