SOIL FORMATION. 135 
the city are closely built residence districts, and the areas toward the 
Pacific Qcean are covered with cottages, more and more sparsely 
placed, to the boundaries of the county. 
Adjoining the business district on the southwest side, along Mis- 
sion Creek, on the flat sand lots, was another thickly populated 
residence section known as " south of Market street." It was occu- 
pied almost exclusively by wooden buildings. 
More than 90 per cent of the buildings in San Francisco were of 
wood. Almost all the brick, stone, and steel structures were in the 
congested business portions of the city, upon or very near the made 
land. Even in this district there was a large percentage of wooden 
buildings. High steel structures of the most modern type have 
been erected only recently in San Francisco, and the number of them 
is small, not exceeding 50. 
The most destructive effects of the earthquake in San Francisco 
were experienced upon this made land. Wherever buildings were 
well founded on wooden piles deeply driven into the mud — as, for 
example, the Union Ferry Building — these foundations were dis- 
turbed but little or not at all ; and where the superstructure had been 
well and strongly put up, practically no damage resulted. Only in 
poor foundations laid directly upon " filled-in " ground on the raft 
principle, or in buildings that were poorly constructed or under- 
pinned or had a weak frame, poor brickwork, or brick laid dry in 
poor lime mortar, was there serious damage or collapse. 
The Union Ferry Building (PL XLVI, A), with the exception of 
its high tower, was little injured, and the level of its floors was not 
perceptibly changed. At the same time, the streets at its front, which 
rested simply on the made soil, were rolled into waves 3 or 4 feet in 
height. So far as the writer is aware no foundations that had been 
properly established were in any considerable degree injured by the 
earthquake; nor was any structure of brick or stone, iron or steel, 
that was well designed and constructed, greatly damaged. Some 
chimneys and cornices were thrown down, but until the fire had 
passed over the region the structures remained ready for use. This 
statement applies especially to the wooden-frame structures through- 
out the residence part of the city, where the only losses were those of 
chimneys and plaster. 
On the made land in the business portion of the city there had 
been erected in early days many light wooden buildings, which 
rested on simple timber underpinning founded on the filled-in mate- 
rial. Many of these structures collapsed, but this result was due to 
their imperfect foundations and weak construction rather than to the 
severity of the earthquake. Numerous structures in this district 
had been built of dry brick or stone laid in common lime mortal-, 
and their beams, girders, and columns had not been anchored to the 
