These are of very various types of construction, and may be used either for lighting or ventilation, or both combined. When used for lighting, the sashes may be arranged on the sides of the lanterns either as fixed sashes, or made to open on hinges or centres; or, on the other hand, the roof of the lantern may itself be glazed, forming a fixed light. Ventilating lanterns may be constructed either with fixed louvre blades, or with an arrangement of blades made to turn upon a centre, with a common gearing, enabling the ventilation openings to be opened or closed, or placed partially open at discretion. Glazed sashes or solid panels hung on centres will also effect the same purpose of ventilation, while in lanterns with fixed louvres at the sides, an additional subsidiary ridge ventilator, with fixed opening, is frequently added.

Scale 1 inch   1 foot.

Fig. 265. Scale 1 inch - 1 foot.

Scale 1 inch = 1 foot.

Fig. 266. Scale 1 inch = 1 foot.

Scale \ inch = 1 foot.

Fig. 267. Scale \ inch = 1 foot.

Scale half full size.

Fig. 268. Scale half full size.

In buildings of a superior class, a type of ventilation is required ■which shall be reliably weathertight, and this condition is usually met by the construction of sashes in superior joiner's work, with weather bars, grooved sills, or other devices for the proper exclusion of wind and water.

Scale 3 inches = 1 foot.

Fig. 269. Scale 3 inches = 1 foot.

These forms of construction cannot here be further alluded to, but some attention may conveniently be given to a class of ventilating lantern frequently met with in the roofs of machine shops, boiler shops, engine houses, factories, and the like, where ventilation is essential, and where a form of construction may be adopted which, if not absolutely weatherproof, is admissible under the circumstances.

Scale | inch = 1 foot.

Fig. 270. Scale | inch = 1 foot.

Ventilating lanterns of this type are shown in Figs. 271 and 281, of the same form of construction but of different pitches.

Both lanterns have fixed louvres at the sides, a glazed roof, and a subsidiary ridge ventilator.

Scale ⅜ inch = 1 foot.

Fig. 271. Scale ⅜ inch = 1 foot.

The structure of the lantern consists of two sides and one centre standard of cast iron, the side standards being arranged to receive three or four rows of galvanized mild steel or wrought iron louvre blades, together with a special cast-iron sill piece forming the lowermost member of the louvre system, and throwing off the drippings of the louvre blades on to the main roof covering below, which in the figures shown is of zinc on boarding and rolls. The ridge ventilator is framed in timber as shown, and covered with zinc.

Scale  inch = 1 foot.

Fig. 272. Scale inch = 1 foot.

Scale  inch = 1 foot.

Fig. 273. Scale inch = 1 foot.

Side elevations of the side standards are shown in Figs. 261 (four blades), and also in Fig. 262 (three blades). Side elevations of the centre standard are shown in Figs. 263, 264; the former showing details of glazed lantern roof with wood sash bars ; the latter, details of a lantern roof of zinc on boarding.

Scale 1 inch = 1 foot.

Fig. 274. Scale 1 inch = 1 foot.

Fig. 265 is an enlarged detail of the side standard shown in Fig. 262, the blades being removed, and Fig. 266 is a front elevation, showing the provision made for the reception of the cast-iron sill piece mentioned above, and which is intended to catch any rainwater which may creep down between the ends of the louvre blades and the faces of the standard, and throw it off on to the roof covering below. Fig. 267 shows a sill piece in elevation.

Scale 1 inch = 1 foot.

Fig. 275. Scale 1 inch = 1 foot.

The ventilating louvres above referred to are of the fixed type, incapable of being closed, and the slope, dimensions, and overlap of the louvre blades have therefore to be so arranged as to give the greatest possible amount of Watertightness, while preserving a free entrance and exit of air for ventilating purposes.

A large scale detail of the blades and their attachment is given in Figs. 268 and 269, which show the means adopted to secure these requirements, which were successfully attained in the cases under description.

Scale 1 inch = 1 foot.

Fig. 276. Scale 1 inch = 1 foot.