Clinging for a moment to the edge of the tank, he twisted the plank from under Ballard's feet.

Ballard dropped with a splash.
"Merciful powers!" yelled a voice in wild alarm.

"Get him out, quick! That's the solution tank and is filled with cyanide!" Merriwell's heart almost stopped beating.

In a gleam of light from the mill he saw the white, drawn face of Pardo peering toward the spot where Ballard was splashing in the deadly cyanide solution.

An instant later he bounded to the rescue..