BLÜCHER had made so admirable a disposition of his four _Corps d'Armée_, that two of them could at any time have combined, and therefore have presented a superior force to GROUCHY, at any point between Wavre and Planchenoit; whilst the remainder of the Army might have continued its march to the Field of Waterloo. Had Grouchy moved by St Guibert and Moustier upon St Lambert, THIELEMANN's Corps would then have been on the march towards Couture, according to his original instructions; and finding BÜLOW engaged with the Enemy, would have joined him. GROUCHY might then have contrived to hold both these Corps at bay, and thus have reduced the co-operating Prussian force at Waterloo to the two Corps under ZIETEN and PIRCH, besides considerably retarding that co-operation; since without having experienced the effects of any such interruption to the progress of the other Corps, as we have here supposed, these two Generals did not reach the Field of Battle until seven o'clock in the evening of the 18th. Such is the extent of the advantage which, under the circumstances, GROUCHY would have gained by a march from Gembloux upon St Lambert; a most important one, no doubt, as time for pushing the struggle with WELLINGTON, with the whole force at his immediate disposal, before the arrival of the Prussians, was of the most vital consequence to NAPOLEON; and this advantage GROUCHY entirely lost by his march upon Wavre--a march which enabled BLÜCHER to appear with three, out of his four, _Corps d'Armée_, on the great and decisive Field of Action; and that in sufficient time to render the victory as complete as could reasonably be desired. No exertions, however, on the part of GROUCHY, after he broke up from Gembloux on the morning of the 18th, could have effectually frustrated the junction of WELLINGTON and BLÜCHER. Two great errors, for which that Marshal was not accountable, reduced the contemplated junction from a measure of calculation to one of certainty. The first and principal of these has already been adverted to at some length, and cannot be too closely kept in view--the fatal neglect of a vigorous pursuit of the defeated Prussians, on the night of the 16th and morning of the 17th, by a detached Corps; combined with the extraordinary delay in the attack upon WELLINGTON at Quatre Bras, on the latter day. The second error arose from the want of a strong reconnaissance and vigilant look out on the right of the main French Army, on the morning of the 18th, followed up by the occupation of the Defiles of the Lasne. * * * * *