No one knows exactly why it is called the 'Jack,' but it may have been because in the old days, the English knights, when they went out to fight their battles, wore a jacket over their armour with the St.George's Cross upon it, so it would be known to what nation they belonged.

This jacket was sometimes called a 'jack' for short.
"The Union Jack did not become a complete flag as we have it to-day until the year 1801, when St.Patrick's Cross was added to it.

The Stars and Stripes, the flag of my country, was first made in 1776, and on June 14, 1777, it was adopted by the United States Congress as the national emblem, so you see it is even older than the British flag.

The flags of all nations in the world have changed since 1777 excepting only the United States flag, and every American is proud of the fact that his flag is older than the flag of any other Christian nation in the world." The boys, and Thomas and Margaret also, were fascinated with Doctor Joe's brief story of the flags.

They were quite excited with the thought that they were to be a part of the great army of Boy Scouts, and to do the same things that other boys in far-away lands were doing, and the other boys that they had never seen seemed suddenly very much nearer to them and more like themselves than they had ever seemed before.
The three buried their noses in the handbook, now and again asking Doctor Joe questions.