130 THE SAN FRANCISCO EARTHQUAKE AND FIRE. 
elusion and broad statement contained in this report. The only doubt 
in my mind is whether the damage may not have been really greater 
than it appears. 
Extreme caution should be observed in drawing general conclu- 
sions from any individual case of damage in a great conflagration. 
For instance, the way in which misleading conclusions can readily 
be reached is indicated in the discussion of the relative merits of terra 
cotta and concrete for fireproof floor construction. The records of the 
fire, rightly read, would prove that both concrete and burned clay are 
efficient as materials, but that the method of application of both is 
open to severe criticism. That hasty and ill-founded conclusions 
have been reached is only too evident from the articles which have 
appeared since the San Francisco disaster. 
It is also necessary that extreme caution should be observed in 
drawing conclusions in regard to the effect of the earthquake. Reen- 
forced concrete proved itself superior to brickwork beyond any doubt. 
There is every reason to believe that for buildings of moderate height 
reenforced concrete can be so designed that it will be quite as effi- 
cient as a steel frame; but it should be remembered that this propo- 
sition was not proved, because there Avas no reenforced-concrete build- 
ing of considerable height in the entire district affected. Again, the 
fact that steel frames stood up during the earthquake does not prove 
that they are earthquake proof. The framing of the tower of the 
Union Ferry Building suffered almost fatal damage, yet it stood up. 
The Call Building proved the efficiency of stiff and adequate steel 
bracing; but many of the other commercial steel-skeleton buildings 
showed very clearly the need of it. The fact that some of the tall 
buildings are now out of plumb is no proof that they are damaged; 
very few such structures ever are plumb, and if the deviation is not 
very great it is quite possible, even probable, that the building 
was erected out of plumb. The condition of the masonry in wall 
piers, however, gives ground enough for uneasiness. It is safe to 
say that a well-braced steel frame is proof against ordinary earth- 
quakes, but to point to the actual commercial steel-frame structure in 
San Francisco as a triumph of the ordinary t}^pe of steel frame, in 
advance of the careful detailed inspection of the steel work by com- 
petent engineers, is premature, to say the least. 
