-A.K-T GALLERY. In addition to the illustrations of the two oentennial buildings given last week, we here present those of the Art Gallery, Agricultural and Horticultural buildings, with a brief desoription of enen: The Art gallery, which is one of the ftfnxes to the great exhibition, is in the modern renaissance. The uiaterials are granite, glasé, and iron. No wood is used in the construction, and the ing is thoroughly fireproof. The j tura is 305 feet in length, 210 feet in width, and 39 feet in height, over a spaI cious basement 12 feet in height, surmounted by a dome. The main entrauce in the center consists of three colossai arched doorways of equul size. j Two arcades conneöt the pavilions at i the ends with the center ; central seoi tion, 95 feet long, 72 feet high ; pavili. ions, 45 feet long, 00 feet high ; arcades each 90 feet long and 40 feet high. The front of the central aection displays a riso of thirteen steps to the entrence 70 i feet wide. The entrance ia by three arched doorways, eaoh 40 feet high and j 15 feet wide, opening into a hall. Between the arches of the doorways are clusters of colums terminating in emblematic designs illustrative of science and art. The doors, whsch are of iron, are relieved by bronze panels, having the coat-of-arms of all the States and ; Territories. The maiu cornioe is surmounted by a balustrade with candelabras. At either end is an allegorical figure representing science and art. The dome rises from the center ofthe struoture to the height of 150 f eet f rom the ground. It is of glass and iron and of a unique design, terminatlng in a co lossal bell, from which the figure of Columbia rises with protecting hands. A figure of colossal size stands at each oorner of the base of the dome. These figures typifying the four quarters of the globe. The rear or north front is of the same general character. The entire structure covers 3 u acres. HORTICULTURAL BUILDING. The design of the Horticultural building is in the Mauresque style of architecture of the twelfth century, the principie materials externally being iron and glass. The length of the building is 3H3 feet ; width, 193 feet, and height to the top of the lantern, 72 feet. The structure covers 2.5 acres. The main floor is occupied by the central conservatory, 230 by 800 feet, and 55 feet high, surinounted by a lantern 170 feet long, 20 feet wide, and 14 feet high. Running entirely around the con8ervatory, at a height of 20 feet froin the floor, is a gallery five feet wide. On the north and south sides of this prinoipal room are four forcing houses for the propagation of young planta, ; each of them 100 by 30 feet, covered with curved roofs of iron and glass. i Dividing tho two forcing houses in each I of these sides is a vestibule 30 feet square. At the center of the east and west ends are similar vestibules, on I er side of which are the restaurants, reI oeption room, offices, &c. From the vestibulpg ornamental stairways lead to the internal galleries of the conservatory, as well as to the four external j ies, each 100 feet long and ten feet wide, j which surmounts the forcing houses. These external galleries are connected with a grand promenade, formed by the roofs of the rooms on the ground floor, whioh has a superficial área of 1,800 square yards. The east and west entrances are ! proaohed by flights of blue marblo steps from terraces 80 by 20 feet, in the ter of which stands au open kiosque 20 feet in diameter. The angles of the main conservatory are adorned with eight ornamental fountains. The corridors which conneot the conservatory with the surrounding rooms open vistas in every direction. In the basement, which is of fireproof construction, are the kitchen, storerooms, coal-houses, ash-pits, heating arrangenients, etc. This structure U so located as to have a comraanding ïiew of Schuylkill river. AGRICULTURAL BUILDING. Thia structnre will Ilústrate a novel combination of material, and oapable of erection in a few tnonths. Its materials are wood and glass. It consiste of [ a long nave crossed by three transepts, j both nave and transepts being composed of Howe truas arches of a GotUic forra. The nave is 820 feet in length by 125 in width, with a height of 75 feet from the floor to the point of the arch. The central transept is of the same height, and a breadth of 100 feet, the two end transeptB 70 feet high and 80 feet wide. The four courts enolosed betweeu tha nave and transepts, and also the four spaces at the oornera of the building, havinga nave and end transepts for ; two of their sides, will be roofed and i form for valuable spaces for exhibits. j : Thua the ground plan of the building will be a parallelograin of 540 by 820 I feet, coverine a space of above ten acres. In its lminediate vicinity will be the stock yards for the exhibition of horses, cattle, sheep, swine, poultry, etc. There will be required in addition u number of smaller ïtructures for the adininiütratlon of tbe exhibition.