The gray morning broke, and Benner was still at his work. As the daylight dimmed the light of the lamp, he seemed not to notice it, but continued bent over his table, where various blocks, pieces of sheet brass, and a few tools were scattered promiscuously about. A piece of brown paper lay on the floor with what appeared to be a glove. On the corner of the table was a rude imitation of a human hand made of wood, hinged so that the fingers would move. This was not of recent construction; but on a small drawing-board, over which Benner was leaning, was fixed a curious piece of mechanism which he was adjusting, having apparently just put it in working order. He had joined together five pieces of oak-wood, about three quarters of an inch wide and half an inch thick, arranged according to their length. The joints had been cut in the shape of quarter-circles, like the middle hinge of a carpenter’s rule. After these were fitted to each other, a sawcut was made in each one, and a piece of sheet brass inserted which joined the concave to the convex end. Two rivets on one end and one on the other, serving as a pivot, completed the hinge. The joints were so arranged that, when opened to the greatest extent, the five pieces composing the whole made a straight line. The longest piece of wood was fastened at the middle and outer end by screws, which held it firmly to the drawing-board. The shortest piece, on the opposite end of the line, had attached to it on the under side a pointed bit of brass like an index. As morning broke, Benner was engaged in fixing a bit of an ivory metre measure, which is marked to millimetres, underneath this index point. After this scale was securely fastened in its place the mechanism was evidently completed, for he straightened up, looked at his work from a distance, then bent over it again, and gently tried the joints, watching with some satisfaction the index as it moved along the scale. While preoccupied with this study, a sudden knock at the door caused him to start like a guilty man. He threw open the door almost tragically. It was only the concierge, who brought him a letter. He tore it open, and read it and re-read it with eagerness; then went to the table and carefully measured several times the whole length of the mechanism, from the inner screw of the longest piece to the end of the shortest. He then began to calculate and to cipher on the edge of the drawing-board. The letter read as follows: “MONSIEUR,--En fait de renseignements sur la dilatation du bois je ne connais que ceux donnés par M. Reynaud dans son traité d’architecture, vol. i., pages 84 à 87 de la 2ᵉ êdition. “Il en résulte que: “1. Les bois verts se dilatent beaucoup plus que ceux purgés de sève. “2. Que le chêne se dilate tantôt plus tantôt moins que le sapin, mais plus que le noyer.