For small alt-azimuths the ordinary pillar-and-claw stand is sufficiently steady.  For larger instruments other arrangements are needed, both to give the telescope steadiness, and to supply slow movements in altitude and azimuth.  The student will find no difficulty in understanding the arrangement of sliding-tubes and rack-work commonly adopted.  This arrangement seems to me to be in many respects defective, however.  The slow movement in altitude is not uniform, but varies in effect according to the elevation of the object observed.  It is also limited in range; and quite a little series of operations has to be gone through when it is required to direct the telescope towards a new quarter of the heavens.  However expert the observer may become by practice in effecting these operations, they necessarily take up some time (performed as they must be in the dark, or by the light of a small lantern), and during this time it often happens that a favourable opportunity for observation is lost.

These disadvantages are obviated when the telescope is mounted in such a manner as is exhibited in fig. 8, which represents a telescope of my own construction.  The slow movement in altitude is given by rotating the rod he, the endless screw in which turns the small wheel at b, whose axle in turn bears a pinion-wheel working in the teeth of the quadrant a.  The slow movement in azimuth is given in like manner by rotating the rod h’e’, the lantern-wheel at the end of which turns a crown-wheel on whose axle is a pinion-wheel working in the teeth of the circle c.  The casings at e and e’, in which the rods he and h’e’ respectively work, are so fastened by elastic cords that an upward pressure on the handle h, or a downward pressure on the handle h’, at once releases the endless screw or the crown-wheel respectively, so that the telescope can be swept at once through any desired angle in altitude or azimuth.  This method of mounting has other advantages; the handles are conveniently situated and constant in position; also, as they do not work directly on the telescope, they can be turned without setting the tube in vibration.

[Illustration:  Fig. 8.]

I do not recommend the mounting to be exactly as shown in fig. 8.  That method is much too expensive for an alt-azimuth.  But a simple arrangement of belted wheels in place of the toothed wheels a and c might very readily be prepared by the ingenious amateur telescopist; and I feel certain that the comfort and convenience of the arrangement would amply repay him for the labour it would cost him.  My own telescope—­though the large toothed-wheel and the quadrant were made inconveniently heavy (through a mistake of the workman who constructed the instrument)—­worked as easily and almost as conveniently as an equatorial.