The Centre of the à Mont Saint Jean, ainsi manoeuvrez English Army is at Mont St Jean, pour joindre notre Droite. so manoeuvre to join our Right. "Le Duc DE DALMATIE. "The Duke of DALMATIA. "P.S.--Une lettre qu'on vient "P.S.--A letter which has just d'intercepter porte que le Général been intercepted states that General BÜLOW doit attaquer notre Flanc. BÜLOW is about to attack our Flank. Nous croyons apercevoir ce Corps We believe we see this Corps on sur les Hauteurs de Saint Lambert; the Heights of Saint Lambert; ainsi ne perdez pas un instant pour therefore lose not an instant in vous rapprocher de nous et nous coming nearer to us and joining us, joindre, et pour écraser BÜLOW and in crushing BÜLOW whom you que vous prendrez en flagrant délit." will take in the very act." The above letter is of much historical importance. Although conveying NAPOLEON's approval of GROUCHY's movement upon either Corbaix or Wavre, it clearly indicates the commencement of that anxiety and uneasiness of mind which the Emperor experienced through the fear of even the possibility of a want of just conception on the part of the Marshal, of the true spirit in which the combination of his movements with those of the main Army should be carried on. He draws the Marshal's attention to the necessity of his manoeuvring so as to prevent the execution of any hostile design against the Right Flank of the main Army, which is then engaged with WELLINGTON's forces, and names Mont St Jean, the Centre of the Duke's position, as a guiding point. This anxiety was naturally augmented very considerably by the discovery of BÜLOW's troops, and the postscript accordingly enjoins still more urgently the necessity of a close and active co-operation. Very shortly after the Officer who was the bearer of this despatch had started, a message was sent in by General DOMON to the effect that his Scouts had fallen in with Detachments from the Enemy in the direction of St Lambert; and that he had just sent out Patrols towards other points to obtain intelligence of Marshal GROUCHY, and to communicate with him, if practicable. It is to be observed, however, that the troops discovered by the French Cavalry did not belong to BÜLOW's main body, but merely to his Advanced Guard. The former was the mass first seen from La Belle Alliance, when it was moving across the Heights of St Lambert, on the right or opposite bank of the Lasne; but as explained in a preceding Chapter, it encountered great obstruction and much delay during its march towards the Field: whilst the latter, awaiting its arrival, rested concealed in the Wood of Paris, near Lasne.