The Duke then took a general survey of the Field, and while sweeping the horizon with his telescope, he discovered a French Vedette on some rising ground, in the direction of Fleurus, and a little to the right of the high road leading to Namur, apparently belonging to some Picquet thrown out from NEY's extreme Right on the previous night, after the battle had ceased; or to some detached Corps placed in that quarter for the purpose of observation, and for the maintenance of the communication between NAPOLEON and NEY. The Duke had received no intelligence of BLÜCHER; and, probably, judging from the advanced position of the Vedette in question that whatever might have been the result of the Battle of Ligny, the Prussians could not have made any forward movement likely to endanger NEY's Right, he came to the conclusion that it was quite possible that, on the other hand, NAPOLEON might have crossed the Namur road, and cut off his communication with BLÜCHER, with the design of manoeuvring upon his Left and Rear, and causing him to be simultaneously attacked by NEY. His Grace therefore desired VIVIAN to send a strong Patrol along the Namur road to gain intelligence respecting the Prussian Army. A Troop of the 10th Hussars, under Captain GREY, was accordingly despatched on this duty, accompanied by Lieutenant Colonel the Hon. Sir ALEXANDER GORDON, one of the Duke's Aides de Camp. As the Patrol advanced along the road, the Vedette before mentioned began to circle, evidently to give notice of the approach of an Enemy, and then retired. This induced the Patrol to move forward with great caution, so as to guard against the possibility of being cut off. Nevertheless it continued, but with all due precaution, advancing along the road, until after passing a few scattered cottages, comprising a hamlet called Petit Marbais, it reached, about a mile and a half further on, some rising ground, about five miles from Quatre Bras, and beyond which was another height. A Vedette was observed posted upon the latter, but who had evidently not yet discovered the approach of Captain GREY's Troop. Down in the intervening hollow was an isolated house, at the door of which stood a dismounted Sentry, and some horses were standing in an adjoining yard.