Certain species of these army ants which inhabit tropical America, Mr. Belt considered to be the most intelligent of all the insects of that part of the world.  On one occasion he noticed a wide column of them trying to pass along a nearly perpendicular slope of crumbling earth, on which they found great difficulty in obtaining a foothold.  A number succeeded in retaining their positions, and further strengthened them by laying hold of their neighbors.  They then remained in this position, and allowed the column to march securely and easily over their bodies.  On another occasion a column was crossing a stream of water by a very narrow branch of a tree, which only permitted them to go in single file.  The ants widened the bridge by a number clinging to the sides and to each other, and this allowed the column to pass over three or four deep.  These ants, having no permanent nests, carry their larvae and pupae with them when marching.  The prey they capture is cut up and carried to the rear of the army to be distributed as food.

—­Robert Brown:  Science for All.

+Theme C.+—­Present all the evidence you can either to prove or disprove one of the following propositions:—­

Select some question of local interest as:—­
  1.  The last fire in our town was of incendiary origin.
  2.  The football team from ——­ indulged in “slugging” at the last game.
  3.  Our heating system is inadequate.
  4.  It rained last night.

If you prefer, choose one of the following subjects:—­
  1.  The Stuart kings were arbitrary rulers.
  2.  The climate of our country is changing.
  3.  Gutenberg did not invent the printing press.
  4.  The American Indians have been unjustly treated by the whites.
  5.  Nations have their periods of rise and decay.

(Are the facts you use true?  Are they pertinent?  Do you know of facts that would tend to show that your proposition is not true?)

+182.  Number and Value of Reasons.+—­Although a statement may be true and pertinent it is seldom sufficient for proof.  We need, as a rule, several such statements.  If you are trying to convince a friend that one kind of automobile is superior to another, and can give only one reason for its superiority, you no doubt will fail in your attempt.  If, however, you can give several reasons, you may succeed in convincing him.  Suppose you go to your principal and ask permission to take an extra study.  You may give as a reason the fact that your parents wish you to take it.  He may not think that is a sufficient reason for your doing so, but when he finds that with your present studies you do not need to study evenings, that one of them is a review, and that you have been standing well in all your studies, he may be led to think that it will be wise for you to take the desired extra study.

While we must guard against insufficiency of reasons, we must not forget that numbers alone do not convince.  One good reason is more convincing than several weak ones.  Two or three good reasons, clearly and definitely stated, will have much more weight than a large number of less important ones.