io6 



NATURE 



[July 21, 1923 



the local sidereal time. The right ascension damp is 

 released and the telescope shifted until the reading 

 microscope shows the right ascension of the star. 

 The right ascension is then clamped and the dome 



the quick motion in right ascension. The slow motion 

 is controlled by the observer alone, who also holds in 

 his hand means of adjusting the clock rate. Both 

 co-ordinates of a star are read very easily from the eye 



Fig. 2. — Equatorial with steel tube. 



opened. The rising floor has a range of twelve vertical 

 feet — it is not circular, and in azimuth it extends over 

 1 20° but always opposite the dome opening ; for example, 



end, where there is a choice of three breech-pieces — one 

 visual with four oculars, a second with a Repsold 

 micrometer, and a third the photographic, made by 



Fig. 3. — Eye-end 26-inch ri 



when the telescope is pointing to N. 270° E. the rising 

 floor or platform lies between N. 30° E. and N. 150° E. 

 Observers being scarce, provision is made to save them 

 from walking over the edge. In actual work an assistant 

 will stand at the north end of the base and in charge of 



NO. 2803, VOL. 112] 



Adam Hilger to a specification and design by Sir David 

 Gill. No digging for a foundation is required ; the 

 pier will be bolted directly to an outcrop of solid rock. 

 It remains to add a few words on the environment of 

 this much-needed addition to the meagre list of large 



