Xerxes' Pontoon Bridges Xerxes' Pontoon Bridges Xerxes' Pontoon Bridges were constructed in 480 BC during the second Persian invasion of Greece upon the order of Xerxes I of Persia for the purpose of Xerxes’ army to traverse the Hellespont (the present day Dardanelles) from Asia into Thrace, then also controlled by Persia (in the European part of modern Turkey). The bridges were described by the ancient Greek historian Herodotus in his "Histories", but little other evidence confirms Herodotus' story in this respect. Most modern historians accept the building of the bridges as such, but practically all details related by Herodotus are subject to
Suspension (vehicle) Mini. A number of different types of each have been used: Traditional springs and dampers are referred to as passive suspensions — most vehicles are suspended in this manner. The majority of land vehicles are suspended by steel springs, of these types: Automakers are aware of the inherent limitations of steel springs, that they tend to produce undesirable oscillations, and have developed other types of suspension materials and mechanisms in attempts to improve performance: The shock absorbers damp out the (otherwise simple harmonic) motions of a vehicle up and down on its springs. They also must damp out much of