BLÜCHER had quitted Wavre before eleven o'clock in the forenoon, and repaired to the vicinity of Limale, in order to make himself acquainted with the nature of the country in the direction of St Lambert. Whilst here, he received intelligence of the approach of the Enemy towards Wavre. Colonel CLAUSEWITZ, Chief of the Staff of the Third Corps, was immediately made the bearer of an Order for THIELEMANN to defend the position at this place, in the event of the Enemy advancing in force; but, should the latter cross the Dyle higher up the stream, or not appear in great strength (a point concerning which nothing positive was then known), he was to leave only a few Battalions in position at Wavre, and to follow the main Army, with his Corps, as a Reserve, in the direction of Couture. * * * * * GROUCHY's movements, on the 17th and 18th, form so striking a feature in the history of this Campaign, and exercised so important an influence upon the fate of the decisive Battle of Waterloo, that it becomes an essential point in the study of that history, to examine how far he complied with, and carried into effect, the instructions received from his Master, and to what degree his proceedings, consequent upon his ascertaining the direction of the Prussian retreat, coincided with the general plan and object of NAPOLEON's operations. On a reference to the account of his transactions during the 17th, given in the despatch written at ten o'clock on that night, it appears he was completely ignorant of the line by which the principal mass of the Prussian Army had retreated, namely, that of Tilly and Gentinnes, by ZIETEN's and PIRCH's Corps, although his Cavalry had driven back the Prussian Detachment from the latter place to Mont St Guibert, but from whence it appears to have been withdrawn in the night. His attention seems to have been much less devoted to this quarter than it was to his Right, in which direction he detached as far as Perwès. The main body of his forces did not proceed further than Gembloux on the 17th, that is, about five miles from the Field of Ligny.