HOW TO WORK WITH THE TELESCOPE. 
289 
will still remain, and tlie distinctness of tlie view will be 
increased. In like manner, when bright and close double 
stars are to be observed, the aperture of the object-glass 
should be diminished. But when the less brilliant planets 
— Saturn, Uranus, and Neptune — are to be observed, or when 
Mercury and Yenus are to be observed in full twilight or by 
daylight, or any of the planets with high powers, the full 
illuminating power of the telescope may be applied. In like 
manner, when unequal or faint double stars are observed, the 
aperture must not be diminished. 
Here for the present I must conclude, hoping in a future 
paper to point out the objects of interest which the possessor 
of a telescope of moderate power may profitably examine, and 
to show how they may be observed to the best advantage. I 
shall also venture to point out some paths in which the patient 
and systematic observer, even with low or moderate instru- 
mental power, may hope to effect useful, if not important, 
discoveries, — to do “ yeoman’s service 33 in the ranks of our 
scientific investigators. 
