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a hole just in front of the bearing, of the altitude rod. These holes are connected by a hollow bearing in which a clamping piece slides. When the eccentric is revolved, it presses the clamping piece against the altitude rod, fixing it in any required position. The handle by means of which the eccentrical clamping rod can be revolved works in a bearing fixed to the upper end of the altitude rod, and therefore easily accessible at any elevation.

The second motion in the Alt-azimuth Stand will be indicated by the latter portion of the word, namely, Azimuth, and is obtained as follows :—The strong iron disc which forms the upper fitting of the legs has its surface accurately turned. On this revolves an iron disc, rather less in diameter, to which the bearings which support the trunnions of the telescope are attached. The main axis of this disc passes through the centre of the lower disc, and then through a hollow bearing tube, a continuation of it. All these fittings having been most carefully turned and ground together, great steadiness, combined with facility of horizontal movement, is ensured. In order that this motion may be communicated as evenly as possible, resource must be again had to a screw which is thus applied:— The circumference of the lower disc has an endless screw cut. on it, in which works a tangent screw, which can be easily thrown in and out of action. The advantages of this plan are many, the most important being the rapidity and ease with which the telescope can be shifted from one object to another, even to those in contrary directions ; all that is necessary being to release the clamp and turn the telescope to the object required. The clamp, being carried round with the upper disc, can be fixed directly the desired position is obtained, when the screw is at once in action. Motion is applied to the screw by means of a Hook’s joint, named thus from its inventor. This joint being furnished with a long handle, enables the observer, by means of it, to move the Telescope in Azimuth without removing his eye from the eye-piece.

It will be seen from the preceding remarks that, by the means of the vertical and horizontal screw motions the telescope can be moved in any direction with the greatest facility, permitting a celestial object to be observed with high powers for a considerable time, and with the greatest pleasure and comfort to the observer.

This stand can be taken to pieces in a few minutes, and thus carried indoors after the observer has finished his evening’s work. The operation is best performed as follows: the speculum in its cell having been first removed and covered up, release all the clamps and detach the altitude rod and eccentric from the tube. Resting the tube on the left arm, and grasping the handle with the right hand, it can be lifted from the trunnion-bearings and carried to its destination. The altitude rod and Hook’s joint should be next taken, and then the upper disc, with its fittings, can be lifted from its bearings and removed, leaving the legs for a final load.

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Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,77 %.

La langue de reconnaissance de l'OCR est l'Anglais.

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