Dear Sir: The great interest you take in all things relating to horticulture and the universal popularity of your journal, induces me to send you a plan of ventilation for permanent roofed greenhouses, which I think is superior, in many respects, to any I have yet seen. The construction is simple, not. likely to get out of order, is easily regulated, and can be opened in any weather, from the inside. Being in the highest point of the house, and continuous from end to end, it affords a greater escape of foul or heated air, and operated equally on all parts of the house at once; the caps, when open, being directly over the opening, protect the plants under it from excess of moisture during pro* tracted rains. You will perceive that the sash bars are raised, by the stretchers, clear of the rafters, thus increasing the opening at the ridge, and affording a free circulation of air, lengthwise, immediately under the glass, which, if not of any material benefit to the air of the house, is calculated to preserve the frame from decay, as the less joining of wood about a greenhouse the more durable it will be. To illustrate the drawing, let a be the ridge. 6. Rafter, c. Stretcher, or running raft, on which rest the sash bars (d). e.

The sides of ventilator, into which is framed the upper end of the sash bars, being narrowed to the under side of sash bars between the rafters, as shown on Fig. 3. /. Caps covering the opening half dovetailed and hinged together as shown in Fig. 4. g. The gutter into which is framed the lower end of sash bars. A. Iron rod passing through the ridge, and secured firmly to the cap, the lower end connecting with the lever under the staging, as in Fig. 1. i. -An attachment to be applied when a passage-way is required through the centre of the house, or to suit the construction of the staging, one end scoured to the rod, the other end secured to the lever under the staging by a stout wire (see Figs. 2 and 1). jj. Levers under the staging operating on the cap, opening it any distance required, and secured, up or down, by stationary or movable pins placed in the frame of staging.

We have lately erected a greenhouse in connection with our place of business according to this plan of construction, drawn by Gamaliel King, Esq., Architect, of Brooklyn, N. Y., and find that it answers the purpose admirably.

Any further explanation you may deem requisite will be cheerfully given, and any improvements that may be suggested will be as gladly received.

Very respectfully yours, Andrew Bridgeman.