. This was possible, as the Compromise Tariff (p. 248)
came to an end in that year.

[Sidenote: Northeastern boundary dispute.]

[Sidenote: The Ashburton Treaty, 1842.]

320. Treaty with Great Britain, 1842.--Perhaps the most important
event of Tyler's administration was the signing of the Treaty of 1842
with Great Britain. Ever since the Treaty of Peace of 1783, there had
been a dispute over the northeastern boundary of Maine. If the boundary
had been run according to the plain meaning of the Treaty of Peace, the
people of Upper Canada would have found it almost impossible to reach
New Brunswick or Nova Scotia in winter. At that time of the year the St.
Lawrence is frozen over, and the true northern boundary of Maine ran so
near to the St. Lawrence that it was difficult to build a road which
would be wholly in British territory. So the British had tried in every
way to avoid settling the matter. It was now arranged that the United
States should have a little piece of Canada north of Vermont and New
York and should give up the extreme northeastern corner of Maine. It was
also agreed that criminals escaping from one country to the other should
be returned. A still further agreement was made for checking the slave
trade from the coast of western Africa.

[Illustration: JOHN TYLER.]

[Illustration: THE FIRST MORSE INSTRUMENT.]

[Sidenote: The Morse code.]

[Sidenote: First telegraph line, 1844.]

[Sidenote: Usefulness of the telegraph, _McMaster_, 372.]

321. The Electric Telegraph.--Benjamin Franklin and Joseph Henry
made great discoveries in electricity. But Samuel F. B. Morse was the
first to use electricity in a practical way. Morse found out that if a
man at one end of a line of wire pressed down a key, electricity could
be made at the same moment to press down another key at the other end of
the line of wire. Moreover, the key at the farther end of the line could
be so arranged as to make an impression on a piece of paper that was
slowly drawn under it by clockwork. Now if the man at one end of the
line held his key down for only an instant, this impression would look
like a dot. If he held it down longer, it would look like a short dash.
Morse combined these dots and dashes into an alphabet. For instance, one
dash meant the letter "t," and so on. For a time people only laughed at
Morse. But at length Congress gave him enough money to build a line from
Baltimore to Washington. It was opened in 1844, and pro