The drawing room, another enchanting place, is of a circular form, surrounded with Ionic pillars. In the intercolumniations, are arches lined with mirrors, and ornamented with the most tasteful hangings. Under each arch is a sopha. The ceiling represents caryatides supporting a circular gallery, between which are different subjects, such as the Toilet of Venus, the Departure of Adonis, &c. Every thing here is gallant and rich; but mark the secret wonder. You pull a string; the ceiling rises like a cloud, and exhibits to view an extensive sky, with which it becomes confounded. The music of an invisible orchestra, placed above the ceiling, used to be heard through the opening, and produced a charming effect, when entertainments were given in these apartments. This is not all. You pull another string; and, by means of concealed machinery, the aperture of the three casements suddenly becomes occupied by pannels of mirrors, so that you may here instantly turn day into night. The bed-chamber, the _boudoir_, the study, &c., are all decorated in a style equally elegant and tasteful. LETTER XXIII. _Paris, November 25, 1801._ Of all the public edifices in this capital, I know of none whose interior astonishes so much, at first sight, and so justly claims admiration, especially from those who have a knowledge of architecture or mechanics, as the HALLE AU BLÉ. This building is destined for the reception of corn and flour: it was begun in 1762, on the site of the ancient _Hôtel de Soissons_, which was purchased by the city of Paris. In the space of three years, the hall and the circumjacent houses were finished, under the direction of the architect, CAMUS DE MEZIÈRE. The circular form of this hall, the solidity of its construction, its insulated position, together with the noble simplicity of its decoration, perfectly accord with the intention and character of the object proposed. Twenty-five arches, all of equal size, serve each as an entrance. On the ground-floor are pillars of the Tuscan order, supporting vast granaries, the communication to which is by two stair-cases of well-executed design. The court is covered by a cupola of one hundred and twenty feet in diameter, forming a perfect semicircle, whose centre, taken on a level with the cornice, is forty-four feet from the ground. The dome of the Pantheon at Rome, which is the largest known, exceeds that of the _Halle au Blé_ by thirteen feet only. This cupola is entirely composed of deal boards, a foot in breadth, an inch in thickness, and about four feet in length. It is divided into twenty-five lateral openings, which give as many rays of light diverging from the centre-opening, whose diameter is twenty-four feet. These openings are all glazed, and the wood-work of the dome is covered with sheets of tinned copper.