“Let’s put our ears to the ground, Ned,” said he.

The two stretched out ear to earth, and then Ned not only heard the noise much more distinctly, but he knew at once what it was.  He had heard it more than once in the marching army of Cos.  It was the sound made by the approaching wheel of a cannon.

“Artillery,” he said in a whisper.

“Beyond a doubt,” said Karnes.  “It means that the Mexicans have crossed the river—­there’s a ford two or three hundred yards above—­and mean to attack us.  It was your good ear, Ned, that gave us the first warning.”

Ned flushed with pleasure at the compliment, but, a moment or two later, they saw dark figures rising out of the prairie and advancing toward them.

“Mexicans!” cried Karnes, and instantly fired at a dusky outline.  The figures flitted away in the dusk, but the camp of Bowie was aroused at once.  Inside of a minute every man was on his feet, rifle in hand, facing the open place in the horseshoe.  They knew that they could not be attacked from the river.  Bowie came to the side of Ned and Karnes.

“What is it?” he asked.

“Ned heard a sound,” Karnes replied, “and when we put our ears to the earth we knew that it was made by artillery.  Then I saw their scouts and skirmishers and fired upon them.  They must have crossed the river in strong force, Colonel.”

“Very likely,” said Bowie.  “Well, we shall be ready for them.  Henry, you and Smith and the Ring Tailed Panther scout across the prairie there, and see what has become of them.”

“Can’t I go, too?” asked Ned.

Bowie patted him on the shoulder.

“You young fire eater!” he replied.  “Haven’t you done enough for one night?  You gave us the first warning that the Mexicans were at hand.  I think you’d better rest now, and let these old boys do this job.”

The three chosen men disappeared in the darkness, and Ned sat down among the trees with Obed.  They, like everybody else, waited as patiently as they could for the reports of the scouts.

“Obed,” said Ned, “do you think we’re going to have a battle?”

“The signs point that way.”

Bowie set everybody to work cutting out undergrowth, in order that they might have a clear field for the work that they expected.  By the time this task was completed the scouts returned and their report was alarming.

The Mexicans had crossed the river in heavy force, outnumbering the troop of Texans at least five to one.  They had artillery, infantry and cavalry, and they were just out of range, expecting to attack at dawn.  The avenue of escape was cut off already.

“Very good,” said Bowie.  “We’ll wait for them.”

It was too dark to see, but Ned knew that his blue eyes were glittering.  He advanced to the point where the bluff rose nearly ten feet to the edge of the prairie, and took a long look.

“I can see nothing,” he said, “but I know you men are right.  Now we’ll cut steps all along the edge of this bluff, in order that our men can stand in them, and fire at the enemy as he comes.  Then we’ll have as fine a fort here as anybody could ask.”