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.