1894.] on the Astronomical Telescope. 319 



the two large observatories built since in the United States, viz. the 

 Washington and the Chicago Observatories. The Lick Trustees, 

 however, rejected the proposals for the employment of motors for the 

 equatorial movements and dome. That experience gained since the 

 construction of this telescope has confirmed the correctness of my 

 views as respects the desirability of adopting this system is evident, 

 as, in their latest and most perfect instrument, that of the Yerkes 

 equatorial at Chicago, practically all the suggested improvements in 

 that model exhibited before you in 1886 have been adopted, and I 

 hope will contribute in no small degree to the quautity as well as the 

 quality of the output of work we may expect from that splendid 

 instrument ; but to show that this by no means represents all that 

 can be done in this direction, I have here a rough and unfinished 

 model of an observatory in which the principle is carried still 

 further. 



It will be observed that in the Lick design the astronomer is 

 relieved of all physical exertion, but still his attention is required 

 during all the process of setting of the instrument. In our latest 

 design we are able to relieve the astronomer of even the mental 

 strain in this way. In some of our modern equatorials the setting of 

 the circles can be placed (by a new arrangement) at the eye end of 

 the telescope. Suppose this to be so arranged in the large telescope 

 and that an arrangement be added something similar in principle to 

 the steam steering gear of our large steamers, with which every one 

 is now T familiar. In this machine the construction is such that when 

 a small light wheel is turned any quantity to port or starboard the 

 motors are automatically set to work and force the helm over in the 

 right direction, and do not stop until the position of the helm itself 

 exactly corresponds to that of the light guiding w r heel. A very 

 simple arrangement of electrical contacts suffices to etfect this in the 

 case of the telescope, and the working of the instrument is effected 

 thus : — 



The astronomer decides what AR and what DEC he desires the 

 telescope to be set at, he walks over to the eye end of the telescope, 

 which, as will be seen further, can only be at a convenient height 

 from the floor, and sets a pair of pointers at the eye end to the 

 particular readings he wishes, and then presses a button to start the 

 motors and " awaits developments." 



Without any more attention from the astronomer the instrument 

 now sets itself in exactly the position he requires, the motors 

 continuing to revolve the telescope on its axes till that position is 

 attained, and then they stop. Meanwhile as certain contacts are 

 arranged at the upper end of the tube connected with the motor 

 which drives the dome, and at the lower end with motors which elevate 

 and depress the floor, the dome revolves if necessary and keeps the 

 opening opposite the upper end of the telescope, while the floor rises 

 and falls as may be necessary, always keeping at a convenient distance 

 below the eye end ; and so, as I said, without any attention or 

 physical or mental strain on the part of the observer, he finds after a 



