straight line, but instead of being upright like the perpendicular
line, you see that it is sloping. What does it form? A. One side of
it is an acute angle, and the other side is an obtuse angle. Q. Which
side is the obtuse angle? A. That which is the most open. Q. And which
is the acute angle? A. That which is the least open. Q. What does
acute mean? A. When the angle is sharp. Q. What does obtuse mean? A.
When the angle is less sharp than the right angle. Q. If I were to
call any one of you an acute child, would you know what I meant? A.
Yes, sir; one that looks out sharp, and tries to think, and pays
attention to what is said to him; and then you would say he was an
acute child.

[Footnote b: Mr. Chambers has been good enough to call the instrument
referred to, a gonograph; to that name I have no objection.]

[Footnote B: Desire the children to hold up two fingers, keeping them
apart, and they will perceive they diverge at top and converge at
bottom.]

_Equi-lateral Triangle_.

Q. What is this? A. An equi-lateral triangle. Q. Why is it called
equi-lateral? A. Because its sides are all equal. Q. How many sides
has it? A. Three sides. Q. How many angles has it? A. Three angles.
Q. What do you mean by angles? A. The space between two right lines,
drawn gradually nearer to each other, till they meet in a point.
Q. And what do you call the point where the two lines meet? A. The
angular point. Q. Tell me why you call it a tri-angle. A. We call it a
tri-angle because it has three angles. Q. What do you mean by equal?
A. When the three sides are of the same length. Q. Have you any thing
else to observe upon this? A. Yes, all its angles are acute.

_Isoceles Triangle_.

Q. What is this? A. An acute-angled isoceles triangle. Q. What does
acute mean? A. When the angles are sharp. Q. Why is it called an
isoceles triangle? A. Because only two of its sides are equal. Q. How
many sides has it? A. Three, the same as the other. Q. Are there any
other kind of isoceles triangles? A. Yes, there are right-angled and
obtuse-angled.

[Here the other triangles are to be shewn, and the master must explain
to the children the meaning of right-angled and obtuse-angled.]

_Scalene Triangle_.

Q. What is this? A. An acute-angled scalene triangle. Q. Why is it
called an acute-angled scalene triangle? A. Because all its angles are
acute, and its sides are not equal. Q. Why is it called scalene? A.
Because it has all its sides _unequal_