In regard to fencing and precautions at level-crossings, less rigid requirements may be enforced than with standard railways; and in some cases where trains are likely to be few, it has been provided that the normal position of the gates at crossings shall be across the line.
Large pits are dug across the line of advance of these great insect armies to stop them when in the larval or wingless stage, and even huge bonfires are lighted to check their flight when adult.
The motion of these cylinders across the line of centres is the equivalent of a line doublet along each axis.
There is no " transverse " disturbance, that is, there is in air no motion across the line of propagation, for such motion could only be propagated from one layer to the next by the " viscous " resistance to relative motion, and would die away at a very short distance from the source.
In 1890-91 there was another war - with the Sioux - marked by the battle of Wounded Knee, just across the line in South Dakota.
