undetected because they were carried around on the back of a luggage cart covered with clothes or something soft
No it is known as the underground railroad as it was hidden from sight
1: Underground
The reason she carried a gun was to make sure that the runaway slaves would continue on, because she feared that if she let them go back, that they would give away her route the "underground railroad".
If she let the slave go back the plantation owners would most likely torture him\her into revealing the location of the Underground Railways. This is why she always carried a gun, but never used it.
For esthetic purposes and the process for putting them above ground on private or public land is cumbersome.
Traffic. London Underground runs on electricity.
underground heat
underground heat
Geothermal power
The secret government has many hiding spots underground. They have many cities that are currently underground.
It runs on electricity and it's entirely underground
Power Cords underground.
The products of electrolysis have to be carried with care as the products do not have to mixed again into its orignal form
electrical energy --- electricity
Water always follows the path of least resistance. Just like electricity. It flows downhill. Even underground.
Coal