All day, Sarsfield remained in concealment among the mountains, until, towards evening, the train came in sight, moving slowly with its escort of two troops of dragoons along the high road.  He watched it until it halted, and encamped for the night, in a field beside the highway.  He waited until the horses were picketed, and the men engaged in making their encampment for the night.  Then the Irish cavalry burst down from the glen in which they had been hiding.  The officer in command sounded to horse, but it was too late; before the men were in the saddle, the Irish were upon them, and in a moment the two troops of dragoons were dispersed or killed.

Sarsfield’s men at once set to, to collect the powder waggons, pontoons, and baggage of every description.  The great guns were filled with powder to the muzzle, and then buried two-thirds of their length in the earth.  The whole mass of siege equipage was piled above them, and a train of gunpowder was laid to the store in the centre.  The men then drew off to a distance.  A match was applied to the train, and the whole blew up with a tremendous explosion.

The shock was heard in the faraway camp of William, and he knew that his cavalry had arrived too late to avert the catastrophe he feared.  They had, indeed, just arrived within sight of the spot when the explosion took place.  They rode on at full speed, only to find the vast pile of ruined woodwork blazing furiously.  The Irish cavalry was seen in the distance, leisurely retiring; but, although the English pursued for a short time, the Irish easily evaded them in the darkness among the hills.  The whole of William’s cavalry in camp were sent out, when the explosion was felt, to endeavour to cut off the Irish horse; but Sarsfield was well acquainted with the ground, and retired with his troops safely across the Shannon, having struck a terrible blow against the designs of William.

The king, however, found that, in spite of the measures Sarsfield had taken, two of the guns remained uninjured by the explosion.  These were brought to the camp, and another heavy gun was fetched from Waterford, together with a small quantity of ammunition.  The regiments were at once set to manufacture fascines for the siege, and this work proceeded quickly, the orchards and plantations furnishing an abundance of wood.  The fascines were used for filling up ditches, and the advances against the town were pushed forward with vigour.

But the besiegers were not allowed to carry on their work unmolested, for a constant fire was kept up by the guns on the walls, and the besieged made several sorties, driving back the working parties, destroying their work, and retiring before any considerable bodies of troops could be brought up to attack them.  The three heavy guns were, however, brought into position at a short distance from the wall, and began to play upon it.