which are like bicycle wheels.  Here sits the aviator, and directly back of him is the powerful little engine which sets the propeller whirling at the rear.  The machine makes a noise like a swift-running motor boat or a motorcycle.  It starts off on its wheels and rapidly increases its speed until it rises from the ground and sails away gracefully into the upper air. [Your drawing of Fig. 110 should now be complete.]

“As you look at this machine, remember that it is not at all like a balloon.  The bag of a balloon, filled with gas, is lighter than the air; hence, it stays up without any trouble, unless the bag breaks and lets the gas out.  But the aeroplane has no gas bag; it is heavier than the air and it must ‘keep a-goin’’ in order to stay up at all.  Remember this:  Just as soon as the aeroplane stops, it comes crashing to the earth, like so many have done, bringing death and destruction.

[Quickly detach your drawing paper from your board, turn it one-fourth around and re-attach it with thumb tacks.  With broad strokes of black crayon indicate the foreground.  Add lines of mountains, completing Fig. 111.]

[Illustration:  Fig. 111]

“You boys know how it is when you are riding a bicycle.  Your wheel will stay upright as long as you are pushing ahead, but as soon as you stop the wheel topples over.

“Sometimes the aeroplane engine fails to work, sometimes a wire or rod breaks, sometimes the aviator attempts to do some fancy flying which throws the machine out of balance, sometimes the wind prevents the machine from going on in its course.  Any of these things may cause the machine to stop going forward and come dashing downward.

“You, boys—­and you, girls—­and we older men and women, are just like the aeroplane in one great particular.  In the Christian life, in our work, in our study, in our efforts to do good, we can never hope to succeed and progress if we let anything stop us in the way.  How truly does all this apply to the Sunday School.  The stand-still boy and the stand-still girl never get anywhere.  The stand-still Sunday School is ‘a dead one.’  Life in Sunday School means movement, forward and upward.  If the flying machine stops, it comes crashing to the earth.  If the Sunday School stops, you will also ’hear something drop.’  And the same thing is true of us as Christians.  Praying and psalm singing are not enough.  Backsliding begins when Christians stop working—­stop going forward.  If we would grow, we must go!  And ’keep a-goin’!”

THE PLUM TREE
    —­Mothers’ Day
    —­Training

The Responsibility of Motherhood—­A Lesson From the Tree
Nursery.

THE LESSON—­That constant training and cultivation are necessary to the attainment of excellence in plant life; so, also, the quality of the child depends upon the home training.