On entering the battery they found the men on guard all lying down listening, and were soon at full length with their ears to the ground. All could hear the sound; it was very faint, as faint as the muffled tick of a watch, sometimes beating at regular intervals of a second or so, sometimes ceasing for a minute or two.

"There is no doubt they are mining," Mr. Gubbins said; "the question is, from which way are they coming."

None could give an opinion. The sound was so faint, and seemed to come so directly from below, that the ear could not discriminate in the slightest.

"At any rate," Mr. Gubbins said, "we must begin at once to sink a shaft. If, when we get down a bit, we cannot judge as to the direction, we must drive two or three listening galleries in different directions. But before we begin we must let Major Anderson, of the Royal Engineers, know, and take his advice; he is in command of all mining operations."

In ten minutes Major Anderson was on the ground.

"The fellows are taking to mining in earnest," he said; "this is the third we have discovered to-day, and how many more there may be, goodness only knows. I think you had better begin here," he said to Mr. Gubbins. "You have got tools, I think. Say about six feet square, then two men can work at once. I will be here the first thing in the morning, and then we will look round and see which is the likeliest spot for the fellows to be working from. Will you ask your sentries on the roof to listen closely to- night, in order to detect, if possible, a stir of men coming or going from any given point."