In the centre of another room, dedicated to optics, as we entered, we saw a beautiful nosegay in a vase, which appeared to be composed of the rarest flowers. I approached it with an intention of inhaling its fragrance, when, lo! my hand passed through it. It was an exquisite optical illusion. "Ah!" said my elegant and moralising companion, Madame S----, smiling, "of such flowers has Happiness composed _her_ wreath: it is thus she gladdens with it the eye of Hope; but the hand of Expectation can never grasp it." The graceful moral deserves a more lasting record than it will find in these few and perishable pages. In the other rooms are all sorts of apparatus for trying experiments in the various branches of that department of science, over which Mons. C---- so ably presides. The merit of Mons. C---- has no rival but in his modesty. Considering the rank and estimation which he bears in the republic, his external appearance is singularly unassuming. I have been with him in the gardens of the Thuilleries, when they were thronged with the fashion and gayety of Paris, where he has appeared in a suit of plain brown cloth, an old round hat with a little national cockade in it, under which he presented a countenance full of character, talent and animation. In this homely puritan garb, he excited more respectful curiosity, wherever he moved, than some generals who paraded before us in dresses upon which the tailor and embroiderer had long laboured, and who added to their stature by laced hats entirely filled with gaudy buoyant plumes. From Mons. Charles we went to the church of St. Rocque, in the Rue St. Honore. As we entered, the effect of a fine painting of our Saviour crucified, upon which the sun was shining with great glory, placed at the extremity of the church, and seen through several lessening arches of faint, increasing shade, was very grand. This church has been more than once the scene of revolutionary carnage. Its elegant front is much disfigured, and the doors are perforated, in a great number of places, by the ball of cannon and the shot of musketry. Mass was performing in the church; but we saw only few worshippers, and those were chiefly old women and little girls. From St. Rocque we proceeded to the Hotel des Invalides, the chapel and dome of which are so justly celebrated. The front is inferior to the military hospital at Chelsea, to which it bears some resemblance. The chapel is converted into the Hall of Victory, in which, with great taste, are suspended, under descriptive medallions, the banners of the enemies of the republic, which have been taken during the late war, the numbers of which are immense. The same decoration adorns the pilasters and gallery at the vast, magnificent dome at the end of the hall.