In talking with acrobats, I came upon an interesting phenomenon that seems almost like a violation of the laws of gravitation. It appears that the movements of a performer on the bars or trapeze are affected in a marked degree by the slope of the ground underneath. In other words, although bars and trapeze may rest on supports that are perfectly level, yet the swing of an acrobat's body will be accelerated over a downward slope or retarded over an upward slope. So true is this that the trapeze performer swinging over an upward slope will often require all his strength to reach a given point, while over a downward slope he must hold back, lest he reach it too easily and suffer a collision. Nevertheless, the swing in both cases is precisely the same, with rigging and bars fixed to a true level.
On this point there have been endless arguments, and many persons have contended that acrobats must imagine all this, since the upward or downward slope of the ground under a trapeze can in no way affect the movement of that trapeze. I fancy the wisdom of such people is like that of the professors who proved some years ago that it is a physical impossibility for a ball-player to "pitch a curve." There is no doubt that trapeze performers are obliged to take serious account of the ground's slope in their daily work, to note carefully the amount of slope and the direction of slope, and to take their precautions accordingly. If they did not they would fail in their feats. Those are the facts to which all acrobats bear witness, let scientists explain them as they may.
"Suppose the ground slopes to one side or the other under your trapeze," I asked Ryan, one day. "How does that affect you?"
"It draws you down the slope, and makes your bar swing that way."
"What do you do about it?"
"Sometimes I pull the bar over a little in starting, so as to balance the pull of the hill; but that's uncertain. It's better to fix the rigging so that the bar is a little higher on the downhill side."
Ryan said that a straight-ahead downhill slope is the worst for a man, because he is apt to hold back too hard, being afraid of bumping into his partner, and so he doesn't get send enough, and falls short of his mark.
"But all slopes are bad for us," he said, "and we try hard to get our things put up over level ground."
This is but one instance of the jealous care shown by acrobats for their bars and rigging. These things belong not to the circus, but to the individual performers, who put every brace and knot to the severest test. For the high bars a particular kind of hickory is used with a core of steel inside. Every mesh of the net must resist a certain strain. The bars themselves must be neither too dry nor too moist. The light must come in a certain way, and a dozen other things. Many an accident has come through the failure of some little thing.
This much is certain, that acrobats often suffer without serious injury falls that would put an end to ordinary men. Like bareback riders, they know how to fall, this art consisting chiefly in "tucking up" into a ball and hardening the muscles so that the shock is eased. Also they have by practice acquired the power of deciding instantly how to make the body protect itself in an emergency.