Lenses of various magnifications can be adapted to the carrier and moved about over the stage.
There are " chromatic differences " of the distances of intersection, of magnifications, and of monochromatic aberrations.
Even in powerful magnifications a good image exists in all parts of a relatively large field, and the free working distance is fairly large.
Where very short focus simple microscopes are employed, using high magnifications, it is imperative to employ a stand which permits exact focusing and the use of a special illuminating apparatus.
Although we now know how the errors of lenses may be corrected, and how the simple microscope may be improved, this instrument remains with relatively feeble magnification, and to obtain stronger magnifications the compound form is necessary.