In these circumstances General Bourbaki considered he must resolve on a retreat. He telegraphed to the Government that by the advice of his generals, and to his deep regret, he had been compelled to take up a position further in the rear, and only hoped that the enemy might follow him. Hence this experienced general could have felt no doubt that his army, its attack on the Lisaine, once gone to wreck, could only escape from a very critical position by an immediate retreat. _January 18th._--This morning the Germans were under arms in their positions of the previous day, the French still in full force before the whole front. It was significant that they were busy in the construction of earthworks. They had evacuated Montbeliard the evening before in disorderly retreat, and now held the country west of the place in strength and entrenched. During this day nothing occurred but a cannonade and small skirmishes. General Keller having been reinforced came up on the right, and as the enemy retired to Etobon he was able to re-occupy Chenebier in the afternoon. Further north, Colonel von Willisen again marched on Ronchamp. In the centre Coutenans was taken possession of, and the enemy driven out of Byans by artillery fire; but on the other hand the Germans could not yet penetrate the belt of forest. On the southern bank of the Allaine General von Debschitz's detachments drove the enemy back beyond the line Exincourt-Croix. In the three days' fighting on the Lisaine the Germans lost 1200, the French from 4000 to 5000 men. In spite of much necessary detaching, and of the threatening proximity of the enemy, the siege-works against Belfort were uninterruptedly carried on, and as soon as the complement of the investing forces was again made up, General von Werder followed the retiring French to Etobon, Saulnot and Arcey. THE ARTILLERY ATTACK ON PARIS. (January, 1871.) In the place of the IInd Corps, which had been assigned to the German Army of the South, there had come up into the Paris front the Ist Bavarian Corps, of which Gambetta had said, "The Bavarians no longer exist." It had made so good use of its time of rest in quarters south of Longjumeau that by the beginning of the New Year it was already restored to a strength of 17,500 men, with 108 guns. It was positioned on both banks of the Seine between the VIth Prussian Corps and the Wuertemberg Division. The Wuertembergers reached from Ormesson to the Marne, from which river the Saxons extended rightward to the Sausset brook, so as to narrow the front of the Guard Corps now that the Moree was frozen over and afforded no cover. The duty of watching so vast a place of arms as Paris had made great demands on the endurance of the troops.