Captain Binns therefore bought a tow-line made of three strands of galvanized wire; and placing iron collars upon the necks of the mules, he fastened the wire to them, and then he got a very strong galvanic battery and put it in the cabin of the boat, attaching it to the other end of the line, forming a circuit.
[Illustration: A PERPLEXED MULE] The first time the mules stopped to reflect, the captain sent a strong current through the wire.

The leading mule gave a little start of astonishment, and then it looked around at the boy upon the tow-path with a mournful smile that seemed to say, "Sonny, I would like to know how you worked that ?" But the mules stood still.

Then the captain turned a stronger current on, and the mule shied a little and looked hard at the boy, who was sitting by whittling a stick.

The captain sent another shock through the line, and then the mule, convinced that that boy was somehow responsible for the mysterious occurrence, reached over, seized the boy's jacket with his teeth, shook him up and passed him to the hind mule, which kicked him carefully over the bank into the river.
The mules were about to turn the matter over in their minds when Captain Binns sent the full force of the current through the wire and kept it going steadily.

Thereupon the animals became panic-stricken.
They began to rear and plunge; they turned around and dashed down the tow-path toward the boat.