Beginning with the defences of the Seine, we have the Fort of Cormeilles, with the Redoubt of Francaville in front, as well as that of Les Cotillons supported throughout by a number of batteries. The strong fortified position of Cormeilles stands at nearly 500 feet above the Seine. The slopes are steep, and for defence these groups are of great power. The Valley of Ermont lies between the great works of Cormeilles and the Forest of Montmorency, but these forts and those of Montlignon and Montmorency, placed on the south-west fringe of the forest, sweep the valley. At the north-east of the forest is the Fort of Domont, and further on a pile covered with trees, another strong defensive group exists, including the Fort of Ecouen and several connected batteries. Southwards are the Forts of Stains and the battery of Pincon Hill. This remarkably powerful fortress, with its dependent defences composed of batteries, permanent trenches, timber-cleared expanses for shooting, and barbed wire fences, render it secure against a surprise attack. To the east of St. Denis there is a low-lying plain showing no favourable point for fortification, but which can be flooded by the Rivers Morée and the Trond. This plain is also exposed to the fire of the Fort of Stains and the battery of the “Butte Pincon,” and the defensive works of Vaujours to the south. The Fort of Vaujours and that of Chelles bar access to Paris in the passage between the “Canal de l’Durque” and the Marne. Higher up the Marne than Chelles, and between that river and the Seine, the Forts of Villiers, Champigny, Sucy, and Villeneuve St. Georges have been constructed. These fortified bulwarks of Paris are exceedingly strong. The defensive lines on the Marne from Chelles to Charenton form a rampart against any surprise rush, and as the positions of Montmorency and between Vaujours and Chelles, the fixed defences, have been greatly strengthened by batteries, felled timber and trenches, wire obstacles, and other devices, a most determined resistance could be made in this “sector” of fortified positions. Some improvised field works have been constructed all round Paris, therefore there is no need to describe them in detail. Between the Seine and Palaiseau there are no permanent fortifications in the wide plain, but no attack could be made in this direction or in the Plain of St. Denis unless the powerful fortifications which can concentrate their fire on these passages had been silenced. The fortifications of an earlier date are completely free from a possible dash and render these zones literal mouse-traps. Like Montmorency, the forts of Palaiseau, Villiers, Haut Buc, Saint Cyr, and the batteries of the Bois de Verrières to the south of Versailles form a real fortress, of which the Fort de Chatillon is the mainstay behind.