An unfortunate incident occurred during the passage of BÜLOW's Corps, through Wavre, which materially impeded the march of the troops. The Advanced Guard, consisting of the Fifteenth Brigade (under General LOSTHIN), with the 2nd Silesian Hussars, and a twelve pounder Battery, had scarcely passed through the town when a fire broke out in the main street, and extended itself with great rapidity. This not only caused a suspension of the march of the main body of the Corps, but created much alarm, in consequence of the great number of ammunition waggons in the place. Every exertion was made to extinguish the fire. The 1st Battalion of the 14th Regiment, under Major LÖWENFELD, and the 7th Pioneer Company, were ordered upon this duty; and after they had encountered considerable difficulty, their efforts were crowned with success. In the mean time the Advanced Guard of BÜLOW's Corps had continued its march, and reached St Lambert by eleven o'clock. The Sixteenth, and then the Thirteenth, Brigade arrived much later; and the Fourteenth Brigade, which formed the Rear Guard, was a long way behind. The Advanced Guard did not wait the arrival of the other Brigades, but proceeded forthwith to cross the Defile of St Lambert. Having effected the passage, which was attended with great difficulty, in consequence of the soft and miry state of the valley, it halted in the Wood of Paris, where it continued a considerable time, waiting for the approach of the main body. Patrols, however, from the 2nd Silesian Hussars, were immediately sent forward to feel for the Anglo-Allied Left, and to reconnoitre the French Right. ZIETEN's Corps (the First) commenced its march, upon the left bank of the Dyle, towards Ohain, about noon. Whilst BÜLOW's Reserve Cavalry, following the Thirteenth Infantry Brigade, was passing through Wavre, French Cavalry had penetrated between the Rear Guard of this Corps, at Vieux Sart, and the Detachment under Lieutenant Colonel LEDEBUR at Mont St Guibert. The 2nd Pomeranian, and the 1st Silesian, Landwehr Cavalry were immediately detached from the Reserve Cavalry of the Corps, to aid in checking the advance of the Enemy. The Prussian Lieutenant Colonel LEDEBUR, who was still at Mont St Guibert, having received intelligence of the approach of the French, decided on commencing his retreat towards Wavre. Lieutenant Colonel SOHR, who had fallen back early in the morning from Mont St Guibert, sent 150 Cavalry and two guns of Horse Artillery as a reinforcement to LEDEBUR. The latter now succeeded in forming a junction with the two Cavalry Regiments detached from the Reserve, as also, subsequently, with the Cavalry Brigade under SOHR, after a slight affair with the Third French Corps (VANDAMME's), whilst making good his retreat to Auzel.