CONSTRUCTION" AND FIRE PROTECTION OE COTTON WAREHOUSES. 35 
most severe fires — the conflagration of Salem, Mass. — is shewn in 
Plate XIX, figure 1. This view shows the exterior of the building 
practically undamaged after the surrounding buildings had been 
destroyed. The interior view (fig. 2 of the same plate) shows 
the complete protection afforded by the tin-clad fire shutter. The 
interior of another building which withstood the test, though the 
contents were entirely consumed, is shown in Plate XX, figure 1. 
Some idea of the effect of fire on hollow clay tile may be gained by 
an examination of Plate XX, figure 2. Here the fire wall is of 
the panel-wall type previously described, the tile panels being carried 
in a frame of reinforced -concrete. The timber and plank floors 
of this building were only slightly charred by the fire which shat- 
tered the tile as illustrated. 
SOME DETAILS OF CONSTRUCTION. 
Emphasis should be given to the previous statement that the de- 
signing should be done by a competent engineer. Reliable engineer- 
ing service is frequently supplied by proprietors of the patented 
systems, but it is best to have the services of a disinterested engi- 
neer who is familiar with the character and cost of the local materials 
to be used. 1 
while entirely satisfactory for exterior use, as for platforms, is not the 
most desirable for use inside as the corners are readily damaged by severe 
fire or broken by trucks. 
While concrete properly reinforced with steel is the best material for 
fire-resistance floors and roofs, it is true that there have been cases of poor 
design and workmanship which failed utterly, and there are isolated instances 
of substantial reinforced concrete structures being damaged by extremely 
severe and prolonged fire. These fires have shown that concrete should be 
cast solidly in place in such manner as to make the building, or large sections 
of it, one solid whole, or monolithic, structure. These tests have further demon- 
strated the necessity of so placing the steel that it will be well protected from 
heat by the surrounding concrete. Such observations have indicated that con- 
crete floor slabs should have a protecting thickness of concrete for the steel 
of 1 inch, while this thickness should be li inch for walls and beams and 2 
inches for very heavy beams, or girders, -and columns. If such protection is 
not provided, a severe fire is likely to result in the steel reinforcement be- 
coming so heated as to stretch, causing serious damage to the structure. 
Floors may extend through division fire walls provided the mechanical de- 
sign is such as to make the floor on either side independently self-sustaining 
in case the floor on the other side of the wall is destroyed. The same con- 
struction may be applied to the roof slab. This involves some modification in 
arrangement of reinforcement, and in some cases additional material. These 
stresses which would arise only in an emergency may be computed on the 
basis of the elastic limit of the materials rather than with reference to the 
usual allowable stresses which should be used in computing the normal working 
load. 
1 Materials for concrete permit of wide variation. The proportions for 
concrete reinforced should usually be 1 part Portland cement, 2 parts sand, 
4 parts stone, and water as required. The stone should be in small pieces 
