was not an automobile in sight. He did not see Chet, doubling up with laughter, on the back of the wagon. He gazed doubtfully at the Hardy boys, who were standing at the curb, trying to conceal their smiles.
"Could 'a' swore I heard a horn," grunted Mr. Billers. Then he tugged at the lines and brought the horses into the middle of the road again.
Instantly the horn shrieked again. This time it was even louder and more insistent than before. It seemed that an automobile was right behind the wagon, clamoring to pass.
Almost automatically, Mr. Billers yanked at the reins and the horses again went to the side of the road.
But again no car went by.
Again Mr. Billers looked behind. Again, to his astonishment, he saw that the roadway was clear.
"Hanged if I didn't think I heard a horn!" exclaimed Mr. Billers, greatly puzzled, as he drove on again. "My ears must be goin' back on me."
But in a few minutes the horn shrieked again. Frank and Joe, who were walking along the sidewalk, keeping abreast of the wagon so as not to miss the fun, chuckled as they saw Mr. Billers once more pull on the reins to guide the horses to the roadside. Then
