122 THE SAN FRANCISCO EARTHQUAKE AND EIRE. 
although for that purpose a specially* designed extra heavy side- 
construction skew back would be better, and should on the whole be 
recommended even in connection with the heavy end-construction 
arches described. It is probable that either a good concrete floor 
with the right kind of ceiling below it, or a heavy tile floor such as 
that herein described, would come through almost any fire with no 
damage except the loss of the ceiling plaster. These two types may 
therefore be taken as equivalent in efficiency; they will probably be 
about equal, also, in first cost. 
It should be added that attic floors and roofs should be as carefully 
designed to resist fire as any other part of a building. This is a 
thing that has rarely been done, and the experience of both Baltimore 
and San Francisco shows that it is absolutely necessary. 
PROTECTION OF OPENINGS. 
While there is no doubt that commercial standards of fireproofing 
are dangerously inadequate, the greatest trouble of all is the fact 
that so little attention is paid to protecting the exterior openings in 
a building. Even a very inefficient type of fire shutter would prob- 
ably have saved some of the buildings in San Francisco, which were, 
as a matter of fact, burned out. A light metal shutter combined 
with a window sprinkler would probably resist a rather fierce fire for 
a long time. Although the failure of the water supply in San Fran- 
cisco might be urged as one reason why a window sprinkler would 
have been of no avail, it is a fact that water can be obtained by driv- 
ing wells into the sand which underlies the business portion of San 
Francisco almost everywhere. Under these circumstances, if the fire- 
proof buildings had been fitted with metal shutters, even no better 
than those in the windows of the hall of records, and if each window 
had been provided with a sprinkler and the building itself with its 
own well and fire pump, it is probable that the fire could have been 
kept out of a large number of the buildings. The protection of 
external openings is by all odds the most important constructive 
problem involved in the efforts to make cities proof against con- 
flagration, and it seems probable that at the present time adequate 
protection of windows and doors is available at a reasonable cost. 
In my judgment, windows protected in the following Avay, even 
without sprinklers, might keep out the fire, though the buildings 
were shut up and abandoned. 
1. The outer opening should be protected with some form of 
rolling steel shutter or, preferably, with a shutter composed of sheets 
of steel sliding in very deep rebates in the walls. The sheets of steel 
should be anchored in these rebates by means of angle irons or rivets 
driven so as to interlock with a bead to be placed in position after 
