A very similar scheme has been successfully tried on reflectors as shown in Fig. 174. The instrument shown is a Browning equatorial of 8½ inches aperture. The cover is arranged to open after the manner of Fig. 173 and the plan proved very effective, preserving much greater uniformity of conditions and hence permitting better definition than in case of a similar instrument peering through the open shutter of a dome. Such a contrivance gets unwieldly in case of a refractor on account of the more considerable height of the pier and the length of the tube itself. But a modification of it may be made to serve exceedingly well in climates where working in the open is advantageous. A good example is the equatorial of the Harvard Observatory station at Mandeville, Jamaica, which has been thus housed for some twenty years, as shown in Fig. 175. This 11 inch refractor, used mainly on planetary detail, is located alongside the polar telescope of 12 inches aperture and 135 feet 4 inches focal length used for making a photographic atlas of the moon and on other special problems. The housing, just big enough to take in the equatorial with the tube turned low, opens on the south side and then can be rolled northward on its track, into the position shown, where it is well clear of the instrument, which is then ready for use. [Illustration: FIG. 174.—Cover for Small Reflector.] The climate of Jamaica, albeit extremely damp, affords remarkably good seeing during a large part of the year, and permits use of the telescope quite in the open without inconvenience to the observer. The success of this and all similar housing plans depends on the local climate more than on anything else—chiefly on wind during the hours of good seeing. An instrument quite uncovered suffers from gusts far more than one housed under a dome, which is really the sum of the whole matter, save that a dome to a slight extent does shelter the observer in extremely cold weather. Even very large reflectors can be housed in similar fashion if suitably mounted. For example in Fig. 176 is shown the 36 inch aperture reflector of the late Dr. Common, which was fitted with an open fork equatorial mounting. Here the telescope itself, with its short pier and forked polar axis, is shown in dotted lines. [Illustration: FIG. 175.—Sliding Housing for 11-inch Refractor.] Built about it is a combined housing and observing stand rotatable on wheels _T_ about a circular track _R_. The housing consists of low corrugated metal sides and ends, here shown partly broken away, of dimensions just comfortably sufficient to take in the telescope when the housing is rotated to the north and south position, and the tube turned down nearly flat southward. A well braced track _WW_ extends back along the top of the side housing and well to the rear. On this track rolls the roof of the housing _X,X,X_, with a shelter door at the front end. [Illustration: FIG. 176.—Sliding Housing for a Big Reflector.]