LESSONS FROM THE VARIOUS TYPES OF BUILDINGS. 151 
worse, were of very poor quality. In contrast to such construction 
were the United States Government buildings — the mint and the 
appraisers' (or customs) building (PL XXVIII, A), in San Fran- 
cisco, and the post-office building in Oakland — all of which were 
either entirely uninjured or very slightly injured by the earthquake. 
These buildings were well designed and constructed with the best 
materials and workmanship, upon foundations that had been tested 
and found strong and satisfactory. The results to both of these 
classes of buildings were fully to be expected. 
As a second class of buildings that suffered badly may be grouped 
{ hose of the oldest type of wooden structure in San Francisco, lightly 
resting upon slim wooden underpinning, which stood upon soft and 
unstable soil or loose, unconsolidated sand. Such houses went down 
at the first shock, as one would naturally expect. In contrast to these 
flimsy structures are the thousands of more substantially constructed 
wooden buildings that still stand intact, except as to chimneys and 
some plastering, all over the unburned part of the city. These 
structures were built fairly well and upon stable foundations; and 
the writer believes from his personal observation that no well- 
founded and well-constructed building of wood in San Francisco 
was injured to a greater degree than those just mentioned. In a 
country subject to earthquakes a strongly framed and well-founded 
wooden house, not exceeding three stories in height, with nondisin- 
tegrating plaster and finish, light tile chimneys, and ample fire pre- 
vention and protection, would seem to be the ideal type of residence 
structure. 
Experience shows that buildings constructed with exterior brick 
walls laid in common mortar, with timber columns and girders, tied 
and braced little or not at all, constitute a third class of buildings 
which are nonresistant to a severe earthquake, particularly if they 
are erected upon a poor foundation. Even if the girders and columns 
are of metal, they are pulled apart, and the walls fall inward or out- 
ward during the shock. Only rich Portland cement, laid with wetted 
brick, and strong joists, ties, and anchorage, endured the stress. 
The behavior of the high steel-frame office buildings, which con- 
stitute the fourth class, has shown that in order to resist perfectly 
the bending moments and shears induced by the swaying due to the 
earthquake movement, such buildings should be stiffened in their 
joints and connections by the best riveting combinations, and knee and 
other bracing, particularly at or near the ground floor. This require- 
ment is of the utmost importance, and so also is the one that the sway- 
ing referred to should be diminished by the liberal introduction of 
diagonal and wind bracing throughout. The proper bracing in the 
lower stories has in some buildings been omitted, on the demand of 
