G. W. Hough on Catuloguing and Charting Stars. 167 
| of easy and simple mechanism, a description of which will be 
| given in this connection. 
In the cataloguing of zone stars with the Oleott Meridian 
Circle, during the year 1862, I found it desirable to have some 
contrivance by which we could observe the same zone, star for 
star, on a subsequent night. In order that we may be under- 
Stood, we add that the clamp arm for giving slow motion to the 
. Telescope in zenith distance, is moved by a screw pressing 
, against its lower end, one revolution of the screw being about 6’. 
Play between the two cog wheels), we could follow the same 
Zone with a deviation of less than 5’. Were the pulleys at- 
tached directly to the screw, we know the error would be still 
d : om this fact, we were led to surmise, that difference of 
declination could easily be read to the tenth of a minute, from 
# Screw head used for giving slow motion to the Telescope, in 
_ ‘*enith distance. ‘ ; 
thinking on this subject, I conjectured that if a cylinder 
ee Were attached to this screw, and a pen be made to move over it 
With a uniform velocity in the direction of its length, we could 
Se Teadily record both Right Ascension and Declination, or, in other 
4 Words, make a map of the stars observed. Owing to incon- 
7 Venience in attaching such an apparatus to our instrument, the 
_ #*** Was not put into execution. ‘ 
gp; Will_now proceed to give a description of the Charting ma- 
we. Fig. 1 is a perspective of the machine, as seen from the 
Hatheast. This apparatus is firmly fastened to the south side of 
... West pier, It is connected with the clamp arm of the Tel- 
“seope by means of the horizontal rod (/), 40 in. in length. 
