"Is there any danger?" asked Andy in some alarm.
"Very much," answered the professor quietly. "A ship, once fairly entangled in the grass or sea weed, seldom gets out. If it is a sailing ship the weed clings to the rudder, making steerage impossible, and even in a strong wind the ship cannot get free of the mass. The grass winds about the propellers of steamships, and holds them as tight as in a vise.
"Sometimes a great storm may tear the mass of weed loose from the bottom of the ocean, and then the ship is free. But the Sargasso Sea is the graveyard of many a fine vessel."
The pumps were set going. Anxiously everyone watched the gage. The pointer never moved, but remained at thirty feet. The Porpoise was caught.
"Well, since we can't go up, let us see if we can go down," said the inventor. "Perhaps we can dive under the sea weed."
The cocks of the tanks were opened and the water rushed in. Under the weight of it the ship should have sunk to the bottom. Instead it remained just where it was, thirty feet below the surface.
"Try the screw again," suggested Andy, "Maybe we can back out."
The big propeller in the tube was started going in a reverse direction, but the Porpoise only moved a few feet and then stopped. To go forward was equally impossible.
The submarine was held fast in the grip of the long, sinuous, snake-like fingers of the terrible sea grass. Weak as one strand was, the thousands combined served to fasten the ship as securely as wire cables would have done. The weeds had entangled themselves all around the craft and refused to let go.
"Well," remarked Mr. Henderson when all efforts had failed. "We must think of a new plan."