tilator should in any case be not less than 12 inches square, and, in the case in question, it should be near the master's seat, not far from the floor, two feet long and eight inches high, and open into a box in the wall of these dimensions, or at least 24 inches by six, extending to the ceiling, where it should communicate with the tin box enclosing the smoke-pipe. If the building have two stories, the ventilator tubes must be carried from the lower, upward, within the wall, and communicate in the upper ceiling with the tin box. The supply of fresh air for the upper room should then be brought in from the side of the house between two joists in the floor, and open beneath the stove or behind the fireplace.

This mode of ventilation will be found much more economical, as well as more certain, than a usual mode of making openings into an attic which has windows into the atmosphere. In the latter, you have a flight of stairs to the attic, an attic floor and two windows; in the other, a wooden tube 12 feet long, and a tin one four or five feet long the attic being left unfinished, or, what would be better, having the ceiling of the schoolroom arched, to em. brace a part of the space of the attic.

The details of construction will be given in the explana tion of the plates

D. Entrance door. E. Entry. F. Fireplace. C. Wood closet. T. Teacher's platform. a. Appara tus shelves. t. Air tube beneath the floor. d. Doors. g. Globes. 7. Library shelves. m. Master's ta ble and seat. p. Passages. r. Recitation seats. s. Scholars' desks and seats. rs. Stairs to recitation rooms in the attic. v. Ventilator. w. Windows. b. Movable blackboard. as Air space behind the Sreplace

A. Air box, 1 foot square, or 24 inches by 6, covered by the pilaster, and opening at the floor, in the ase of the pilaster.

B. Round iron tube, 15 inches in dian eter, being a continuation of the air box, through the centre which passes,

C. The smoke flue, 8 inches diameter

D Caps to keep out the rain