exact positions. 
In the observation of asteroids on the meridian, a great deal 
of time is wasted, especially when the error of the ephemeris 
is considerable. And even when the error is only 2’ or 3' in 
declination, in certain portions of the heavens, it is almost im- 
possible to find the body with a meridian instrument. 
This apparatus affords great facility in finding these bodies, 
when we have an approximate Ephemeris; since it is only ne- 
eessary to observe, on two nights, a short zone of five minutes 
in Right Ascension and 10 minutes in declination. The com- 
parison of these two charts will at once show which is the planet, 
provided it is included within those limits; when, the Ephem- 
eris being corrected, it can be observed on the meridian in the 
usual way. This has already been tested in finding some of the 
old asteroids, using for our Ephemerides Hind’s Supplement to 
the Nautical Almanac. ; 
In our ordinary work, as we observe all stars visible, the limit 
being 13-14 magnitude, it is usually impracticable to observe & 
zone of greater width than 10’ or 12’; and within these limits, 
it is not unusual to find more than 200 stars in one hour of 
Right Ascension. 
In case we wish to extend our observations over more than 
