The buildings, as well as all of the statuary, are made of artificial
travertine, of a smoked-ivory tone.
Real travertine is found in and around Rome, especially at Tivoli.
It is a pure carbonate of lime, a creamy white deposit formed from
dripping water, in stratified form, with cavities and fissures lined
with crystals.
The Colosseum and St. Peter's at Rome are both made of this material.
The imitation travertine made with concrete, and used in the second
story of the Pennsylvania Station in New York in combination with real
travertine of the first story, was invented by Mr. Symmes Richardson of
the firm of McKim, Meade and White of New York. He also brought the real
travertine to America to have it used for the first time in a large
building, the Pennsylvania Station.
Mr. Paul Deneville of New York has most successfully made a plastic
travertine, composed of gypsum from Nevada combined with hemp fiber and
a coloring pigment, which has been applied to all of the Exposition
buildings, producing a most pleasing glareless background under the
sunny skies of San Francisco.
The roofs are covered with imitation tiles, since real tiles would be
too expensive for Exposition purposes.