The principal facade, that which fronts Commerce Dock, from which it is separated solely by a garden laid out on Mâture Place, is the most attractive and most ornamented. Here are located the restaurants, the cafes, the music pavilion, and a few other light structures. Internally, this portion of the Exhibition comprises a vast entertainment hall, brilliantly and artistically decorated with tympans representing the three principal ports of commerce--Havre, Bordeaux, and Marseilles--and with pictures by the best marine painters. It is lighted by an immense stained glass window which fronts Commerce Dock and the garden, and which lets in a flood of soft light. The galleries to the right and left, over Paris Street, are reserved for the exhibitions of the ministers of state and of the large public departments, and for models, specimens, plans, and drawings of war and merchant vessels, and of pleasure boats, and for plans of port, roadstead, and river works. Two endless galleries run to the north and south of Commerce Dock, parallel with Orleans Wharf on the one hand and Lamblardie Wharf on the other. The northern gallery is connected by a foot bridge with the annex of Commerce Place, where is located the colonial exhibition, the center of which is occupied by a Cambodian pavilion, in which are brought together the products of Indo-China and Algeria. For half of their extent, the two galleries are separated from the dock by a promenade provided with seats and covered with a roof. On this promenade, it became necessary to make room for certain belated exhibitors whose products are not affected by the open air. In Commerce Dock are to be seen, floating, specimens of every ancient and modern naval construction, French and foreign, among which are the state convette Favorite and an English three-master converted into a cafe boat. We find here, too, the giant and prehistoric oak of the Rhine, on board of the Drysphore. Commerce Dock is divided into two parts by a foot bridge, which allows the visitors to pass from one side to the other without being compelled to tiresomely retrace their steps. The main entrance to the Exhibition is opposite the portico of the theater, on Gambetta Place. A second entrance is found on Commerce Place in the colonies annex. The others, near the center, are on Orleans Wharf, opposite Edward Larue Street, and on Lamblardie Wharf, opposite Hospital Street and opposite Saint Louis Street. The garden of the Exhibition and the galleries that surround it are illuminated at night by the electric light.--_L'Illustration._ * * * * * OUR COAST DEFENSES. General H.L. Abbott delivered a lecture before the Academy of Sciences in New York, on the evening of March 21, a summary of which is given by the _Herald_ as follows: According to General Abbott, the country needs for its coast defenses: