* * * * * While NAPOLEON was occupied in prescribing his intended order of attack, he received a despatch from Count GÉRARD announcing that Lieutenant General DE BOURMONT, and Colonels CLOUET and VILLOUTREYS, attached to the Fourth Corps, had deserted to the Enemy--a circumstance which induced the Emperor to make some alteration in his dispositions. The morning of the 15th had scarcely broken, when the French Army commenced its march towards the Sambre, in three Columns, from the three bivouacs already mentioned as having been taken up during the previous night. The Left Column advanced from Solre sur Sambre, by Thuin, upon Marchienne au Pont; the Centre from Beaumont, by Ham sur Heure, upon Charleroi; and the Right Column from Philippeville, by Gerpinnes, upon Châtelet. As early as half past three o'clock in the morning, the head of the Left Column came in contact with the Prussian troops in front of Lobbes, firing upon, and driving in, the Picquets of the 2nd Battalion of the 1st Regiment of Westphalian Landwehr, commanded by Captain GILLHAUSEN. This Officer who was well aware that the French troops that had assembled, the night before, in great force in his front, intended to attack him in the morning, had posted his Battalion so as to afford it every advantage to be derived from the hilly and intersected ground it occupied. The French, however, inclined more to their right, and joined other troops advancing along the road to Thuin, which lay on his left. Shortly after, they drove back an advanced Cavalry Picquet; and, at half past four, commenced a fire from four guns upon the Outpost of Maladrie, about a mile in front of Thuin. This cannonade, which announced the opening of the Campaign by the French, was heard by the Prussian troops forming the Left Wing of STEINMETZ's Brigade; but the atmosphere, which was extremely thick and heavy, was most unfavourable for the conveyance of sound; so much so, that the greater portion of the Right Wing of the Brigade remained for a considerable time in ignorance of the Enemy's advance. The firing, however, was distinctly heard at Charleroi; and ZIETEN, who, by the reports which he forwarded on the 14th to WELLINGTON and BLÜCHER, had fully prepared these Commanders to expect an attack, lost no time in communicating to them the important fact, that hostilities had actually commenced.