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rays from stars, &c., this also is entirely a question of temperature. Experiments with our large Newtonians, which seem to be peculiarly susceptible to these disturbances, have proved that their performance is seriously affected by a difference of one degree Fahr. between the temperature inside the building and out of doors. Especially is this felt in summer time, when walls and roof have been raised to a high temperature during the day, and keep on radiating heat far into the night. The question, then, is this: can an observatory be built absolutely and entirely free from those evils, and securing to perfection the desiderata named above? To this it is replied that it can, and that in a manner which secures every advantage at a price that places it within the reach of all who can afford the delights of a telescope.

The Romsey Observatory was the first of a great many that have been erected during the last few years, with uniform success. It has stood unscathed the storms of fifteen winters and the heat of fifteen summers, and it is still perfectly good and sound.

In respect to the two great desiderata mentioned above, it may be stated—(i) That the steel pinions of the sidereal clock are as bright after eight winters as when they were first polished. Yet, strange to say—to clear certain trees,—this little observatory stands in the wettest possible position, over the edge of a large extent of water meadows, and water is continually trickling within twelve inches of its boards. (2). As to the other desideratum. Two Newtonians, of the same size, excellence and kind of equatorial mounting have been repeatedly tried against each other on the same stars, &c., and with the very same eye-pieces, one instrument was in the building, the other outside, ten yards distant, at the same height. If there was any difference it was in favour of the observatory, which perhaps arose from the comfort experienced by the observer, and the quietness of a sheltered eye, to say nothing of the advantage of greater darkness in viewing delicate objects.

The advantages of a wide opening in the roof are manifest, and for reflectors (Newtonian), with which vertical views are easiest and best, it extends beyond the middle of the roof, the ridge of which is not central, but farthest from the opening side, so as to command these views with ease.

Finally, the advantages of this light structure are so abundantly proven that it is earnestly presented to the consideration of the very best observational astronomers.

To construct an Observatory on the Romsey model.

Procure ten good straight posts about 4 inches thick and 8 feet long, set them in the ground in a circle, 10 feet 4 inches in diameter, to a depth of 18 inches. Should it be desired to give the building a rustic appearance the posts may be left with the bark on, but they will last longer if it is removed; the lower ends should also be

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