In most cases a single shot across the bow of a boat sufficed to bring it to land.

One day the _White Cloud_, on her way from Kansas City to St.
Louis, refused to halt until three shots had been fired, the last one grazing the top of the pilot-house.

When brought before General Lyon, the captain of the _White Cloud_ apologized for neglecting to obey the first signal, and said his neglect was due to his utter ignorance of military usage.
The apology was deemed sufficient.

The captain was dismissed, with a gentle admonition not to make a similar mistake in future.
At that time the public was slow to understand the power and extent of military law and military rule.

When martial law was declared in St.
Louis, in August, 1861, a citizen waited upon the provost-marshal, in order to ascertain the precise state of affairs.
After some desultory conversation, he threw out the question:-- "What does martial law do ?" "Well," said Major McKinstry, the provost-marshal, "I can explain the whole thing in a second.