190 RECORD OF SCIENCE FOR 1887 AND 1888. 



circle graduated to 20 seconds and read through a series of i^risiub, at 

 the eye end to 1 seconds.. On the declination sleeve near the tube is a 

 tine declination circle 3 feet in diameter graduated to 5 minutes of arc, 

 and read from the eye end to 12 seconds, while on the outer end of the 

 axis is a coarse declination circle 6 feet in diameter graduated to degrees. 

 The driving clock is regulated by a frictional governor of the cross- 

 armed t^pe and by an electric control from the standard clock. One 

 of the shafts carries a chronograph drum. For photographic work an 

 opening is cut in the side of the tube about 10 feet from the eye end, 

 and a plate 20 inches square can here be inserted and suitably adjusted. 

 The eye end is so arranged that the micrometer can be quickly re- 

 moved and two steel bars inserted in bearings. These bearings are 

 part of a jacket revolving 300° in position anglo, and to them can be 

 attached spectroscopes, photometers, enlarging cameras, etc. The eye 

 end is also surrounded by a large ring, which supports the various 

 liaudles for actuating the clamps and slow motions, and carries the read- 

 ing microscopes and finders as well as a small sidereal chronometer. 

 The clamps and slow motions are operated as follows: 



An observer at the eye end can — 



(1) Clamp in declination. 



(2) Give slow motion in declination. 



(3) Eead the declination circle (two verniers). 



(4) Clamp in right ascension. 



(5) Stop the clock. 



(G) Gire slow motion in right ascension. 



(7) Read right ascension circle (one microscope). 



An assistant on either side of the balcony below the axes can— 



(8) Clauip in declination. 



(9) (iive rapid motion in declination. 



(10) Give slow motion in declination. 



(11) Give quick motion in right ascension. 



(12) Give slow motion in right ascension. 



(13) Clamp in right ascension. 



(14) Stop or start the driving clock. 



(15) Read the right ascension circle (two microscopes). 



(10) Eead a dial showing the nearest quarter degree of declina- 

 tion. 



Detailed drawings of the mounting are given in Engineering, volume 

 46, London, 1888. 



The ahmicantar.—]n volume 17 of the Annals of Harvard College 

 Observatory, Mr. S. C. Chandler, jr., has given a complete description 

 and investigation of his "ahnncantar," and a discussion of a series of 

 observations made with it in 1884 and 1885. The almucantar, as its 

 name implies, is an equal altitude instrument, and was devised by Mr, 

 Chandler in 1879, It consists, essentially, of a telescope attached to a 



