The forth sigh said the land will be crossed by snakes of iron, this sign just indicates the train transportation,
and the snakes of iron corresponds to the train itself,
the movement of train sometimes move in curved path,
and that is how snakes behaves like.
and the trialroad is widespread around the world,
so it also meets the part sign said the that the land will be crossed.
what crossed the land is the trailroad.
The fifth sign is that the land shall be criss-crossed by a giant spider's web.
And this somehow hapeens.
this sign implies our electric power and telephone lines nowadays.
these facillities also spread out the world ,
because it is less restricted by geographical factor,
and their density of the coverage of land match the decription in the sign , it indeed spread everywhere like spider web.
The sixth sign is ,The land shall be criss-crossed with rivers of stone that make pictures in the sun.
this sign describes concrete highways and their mirage-producing effects,
This also includes the sign of the internet and wireless connenction.