In addition to a wing on the eastern side of the old building, and which is now completed, it is proposed to erect a similar edifice on the other side. The plan of the west wing contemplates the construction of each story in one continuous room of sixty-three feet in width, and two hundred and seventy feet in length ; the floors to be supported by arches springing from granite piers in the sub-basement, and from marble piers in the principal and attic stories; in consequence of the great descent of the western half of the Patent Office square, the west wing will have a sub- basement of seventeen feet in height, entirely out of the ground, making one more story in this than in the eastern wing. The architect shows the importance of bringing the centre building, as nearly as possible, into harmony with the wings, and suggests the propriety of altering the basement windows to bring them into conformity with those of the new building. This IS conceived not only necessary to the beauty of the design, but also to the comfort and convenience of the clerks who occupy the rooms they light. Another incongruity in the external appearance is the rock work of the basement of the centre building, standing, as it does, in juxtaposition with the smooth marble basement ot the wing. Mr. Walter recommends, as a method of obviating, as far as possible, this objection, that the rough surface of the granite work be dressed off, and brought as nearly into conformity to the marble as may be done without cutting it into rustics. He expresses the opinion that it would be hazardous to attempt to rusticate this part of the work to correspond with the wing, as it is very doubtful whether the joints would hold good to the depth of the rustics. If, however, the wall is brought to a smooth surface, and painted like the rest of the building, the want of entire I uniformity would not be observed.