Fig. 33. Simple Propagating-oven.
Fig. 34. Propagating-oven.
In all the above appliances heat is obtained from the sun or from the bench-pipes or flues of a greenhouse. There are various contrivances in which the heat is applied locally, for the purpose of securing greater or more uniform heat. One of the simplest and best of these is the propagating-oven shown in [Fig. 33]. It is a glass covered box about two feet deep, with a tray of water beneath the soil, and which is heated by a lamp. A similar but somewhat complicated apparatus is illustrated in Figs. [34], [35], [36]. This is an old form of oven, which has been variously modified by different operators. [Fig. 34] shows a sectional view of the complete apparatus. The box, A A, is made of wood and is usually about three feet square. L is a removable glass top. B represents a zinc or galvanized iron tray which is filled with earth in which seeds are sown or pots are plunged. C is a water tray to which the water is applied by means of a funnel extending through the box. A lamp, D, supplies the heat. A funnel of tin, e e, distributes the heat evenly. Holes should be provided about the bottom of the box to admit air to the flame. A modified form of this device is shown in Figs. [35] and [36]. The water tray, G, slides in upon ledges so that it can be removed, and the heat funnel, L D L, slides in similarly and is made to surround the flame like a chimney. The front side of the apparatus is removable, and the top of the frame, K, is made of metal. The cover for this apparatus is figured in [Fig. 36]. The ends, a a, are made of wood, with openings, indicated by the arrows, to allow of ventilation. The front and top, g g, are made of glass. The frame-work, c c c, is made of metal. The cover is hinged on, or held with pegs, I I, [Fig. 35].
Fig. 35. Modified form of [Fig. 34].