Not long after three o'clock in the afternoon, the Prince of ORANGE arrived in Brussels, and informed the Duke that the Prussian Outposts had been attacked and forced to fall back. His Royal Highness had ridden to the front at five o'clock in the morning, from Braine le Comte, and had a personal interview at St Symphorien, with General VAN MERLEN, whose troops were on the immediate right of the Prussians, who had retired. After having given to this General Verbal Orders respecting his Brigade, the Prince left the Outposts between nine and ten o'clock, and repaired to Brussels to communicate to the Duke all the information he had obtained respecting the Enemy's attack upon the Prussian Advanced Posts. This, however, was not sufficiently conclusive to induce his Grace to resolve upon any immediate step; but, in about an hour afterwards, that is, about half past four, General VON MÜFFLING, the Prussian Officer attached to the British Head Quarters, waited upon the Duke with a communication which had been despatched from Namur by Prince BLÜCHER at noon, conveying the intelligence that the French had attacked the Prussian Posts at Thuin and Lobbes on the Sambre, and that they appeared to be advancing in the direction of Charleroi. The Duke was fully prepared for this intelligence, though uncertain how soon it might arrive. The reports which had been made to him from the Outposts, especially from those of the 1st Hussars of the King's German Legion, stationed in the vicinity of Mons and Tournai, gave sufficient indication that the Enemy was concentrating his forces. But, as observed in the preceding Chapter, his Grace was determined to make no movement until the real line of attack should become manifest; and hence it was, that if the attack had been made even at a later period, his dispositions would have remained precisely the same. The Duke at once gave Orders for the whole of his troops to assemble at the Head Quarters of their respective Divisions and to hold themselves in immediate readiness to march. At the same time an express was despatched to Major General DÖRNBERG, requiring information concerning any movement that might have been made on the part of the Enemy in the direction of Mons. The following were the movements ordered by the Duke. Upon the Left of the Army, which was nearest to the presumed point of attack--PERPONCHER's and CHASSÉ's Dutch-Belgian Divisions were to be assembled that night at Nivelles, on which point ALTEN's British Division (the Third) was to march as soon as collected at Braine le Comte; but this movement was not to be made until the Enemy's attack upon the Right of the Prussian Army and the Left of the Allied Army had become a matter of certainty. COOKE's British Division (the First) was to be collected that night at Enghien, and to be in readiness to move at a moment's notice.