| |
Geographic Distribution of Think Tanks |
 |
Think tanks are most common in the U.S. and also very widespread in Europe. Still they are an international phenomenon, with at least one or two such institutions in nearly every country of the world.
|
|
Roman smoke telegraph network, 150 A.D.
The Roman smoke signals network consisted of towers within visible range of each other and had a total length of about 4500 kilometers. It was used for military signaling.
For a similar telegraph network in ancient Greece see  Aeneas Tacitus' optical communication system.
|
|
|
