A very neat adaptation of the plan is shown in Fig. 180, of which a description may be found in _Popular Astronomy_ =28=, 183. This observatory was about 9 feet in diameter, to house a 4 inch telescope, and was provided with a rough concrete foundation on which was built a circular wall 6 feet high of hollow glazed tile, well levelled on top. To this was secured a ring plate built up in two layers, carrying two circles of wooden strips with a couple of inches space between them for a runway. In this ran 6 two-inch truck castors secured to a similar ring plate on which was built up the frame of the “dome” arranged as shown. Altogether a very neat and workmanlike affair, in this case built largely by the owner but permitting construction at very small expense almost anywhere. Another interesting modification of the same general plan in the same volume just cited is shown in Fig. 181. This is also for a 4 inch refractor and the dome proper is but 8 feet 4 inches in diameter. Like the preceding structure the foundation is of concrete but the walls are framed in spruce and sheathed in matched boards with a “beaver-board” lining. [Illustration: FIG. 180.—A More Substantial “Romsey” Type.] The ring plate is three-ply, 12 sections to the layer, and its mate on which the dome is assembled is similarly formed, though left with the figure of a dodecagon to match the dome. The weight is carried on four rubber tired truck rollers, and there are lateral guide rollers on the plan of those in Fig. 179. The dome itself however, is wholly of galvanized iron, in 12 gores joined with standing seams, turned, riveted, and soldered. There is a short shutter at the zenith sliding back upon a frame, while the main shutter is removed from the outside by handles. [Illustration: FIG. 181.—Detail of Light Metal Dome for Small Observatory.] Observatories of the Romsey or allied types can be erected at very moderate cost, varying considerably from place to place, but running at present say from $200 to $600, and big enough to shelter refractors of 4 to 6 inches aperture. The revolving roofs will range from 9 to 12 feet in diameter. If reflectors are in use, those of about double these apertures can be accommodated since the reflector is ordinarily much the shorter for equal aperture. The sliding roof, not to say the sliding shelter, forms of housing cost somewhat less, depending on the construction adopted. Going to brick may double the figures quoted, but such solidity is generally quite needless, though it is highly desirable that the cover of a valuable instrument should be fire-proof and not easily broken open. The stealing of objectives and accessories is not unknown, and vandalism is a risk not to be forgotten. But to even the matter up, housing a telescope is rather an easy thing to accomplish, and as a matter of fact for the price of a very modest motor car one can both buy and house an instrument big enough to be of genuine service. CHAPTER XI