Another important advantage of this kind of mount for a large size is, that although it has considerable weight, it is very convenient to move and set up, being built of convenient parts, which are easy of separation and removal. The uprights or standards are separate, and are bolted to the bed-plate, the upper and lower discs are readily detached from the stand. The cradle and tube are in this construction separable. The tube of the telescope being suspended over the side of the stand, is in the most convenient position for observing objects at any altitude, as the stand is out of the way and clear of the telescope. The various disadvantages and objections to the driving clock being carried by the telescope are here avoided. The clock, which is large and very powerful, is bolted down to the iron bed-plate, and the telescope, not having to carry the clock or weight, the balance is never altered nor the rate of the clock disturbed, and thus a strong clock, keeping regular time, and working much longer can be used. They will drive 2-1/2 hours. It will be readily understood that a driving clock to enable the instrument to do the most exact and best work must be powerful and a good time-keeper. Lord Lindsay has said that “the clock should have twice as much power as is used,” otherwise the spindles, &c. are pent up, and it is moreover sensible to any extra weight or work being put upon the instrument.

To give an idea of the efficiency and regularity of this clock, I may mention that a Newtonian telescope of 18 inches aperture, intended to carry a photographic camera of 112 lbs. weight, needed no additional provisions to do the extra work, the rate and power not being affected. There is a mechanism in the clock “for making up of time” and in setting the hour circle can be used with a joint handle or hooks as a fine screw-motion, and can be applied whether the clock is going or not. There is also a provision at the foundation for throwing the instrument out of the meridian, to follow the motion of the moon or planets with the clock and “maker up.” The above mounting is equally suitable for “Cassegrains” and “Newtonians,” to both of which forms it has been successfully applied up to 18 inches of aperture. It is well suited for large telescopes.

Fig. 2 is a mounting on the same principle, but with a shorter polar axis, and the column is in one casting. It is well suited for moderate sizes, and the circles, &c. are applied exactly as in Fig. 1, but when a clock is wanted there is no mounting equal to the former.

The “Educational” is a plain 6-1/2 inch, of 4 to 6 feet focus, and is made to this pattern, with revolving body and screw-motion for following. It is made as portable as it can be, and is a steady, good-working instrument, and much approved of.

THE UNIVERSAL ALT-AZIMUTH.

(Fig. 3.)

In this mounting I have seen little or no alteration needful, except that the tube is now made to balance so that the eye-tube can be reached for objects in the zenith without the observer having to elevate himself, and the elevating rod can be clamped without the lever, the legs of the stand are more curved and have more spread in them.

This “Alt-Azimuth” stand has met with much approval; and where portability is of consideration and the observer has to set up and remove the entire instrument after every night’s work, this, or the Angle-Block stand, will be found the most convenient, more so than an equatorial in any form. There is much less weight to remove, and being in three convenient parts is more readily put together and separated in the dark. If the stand and trunnions can be left in the open air a very small covering will serve to protect them, and then the tube alone has to be removed. The equatorial cannot be too highly recommended where it can be a fixture and undisturbed, as when once got into proper adjustments its advantages can then be realised, but not unless it is a permanent fixture. The circles of a portable equatorial can only be used for very rough reading, and consequently the adjustments are never in order, and the readings are of very limited use indeed.

THE IMPROVED “ANGLE-BLOCK” STAND.

(Fig. 4.)