подчеркните причастия IIThe track is one of the basic features

подчеркните причастия II
The track is one of the basic features of a railway. It is also called the
permanent way. In the early days of railroad building the workers first had
to lay temporary tracks to transport the materials to the construction site.
And only after that they laid down the permanent tracks or the permanent
way, as it was called.
The railroad track of today is quite different from the track used in
the early days of railways. The first tracks had no ballast, the rails were
мейд of wood and rested on heavy blocks of granite. Then the wooden rails
were replaced by iron ones, and the granite blocks were replaced by wooden
ties or sleepers. This kind of track, however, was not strong enough for
heavy steam trains. The discovery how to make cheap steel was of great
importance to the railways for, when placed in the same track, steel rails had
a life 15 times as long as iron rails.
The distance between the rails is called the gauge. The standard
gauge in most countries is 1,435 mm while in Russia the railroads have a
gauge of 1,524 mm. That gauge was finally adopted when the first main-line
Moscow St. Petersburg railway was under construction (18421851). Thus
Russia was the world's first country where the uniform gauge was adopted
for all railways. In America, the gauge was unified only in 1886