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.
From this it can be seen that, as a rule, quite slight magnifications suffice to bring all representable details into observation.
Hence the different magnifications of a point 0 1 beyond the axis.
For slight magnifications a revolving plane mirror fixed below the object for altering the direction of the rays suffices.
For slight magnifications rough adjustment is sufficient, but with objectives of a focus below 4 in., a fine adjustment is wanted.
They are often so small that high magnifications may be necessary to ascertain their presence.
Small German periscopes were usually 1 metre or 2 a metre in length and had two eyepieces giving magnifications 10 and 15 diameters.
From this it appears that each observer obtains specific advantages from one and the same simple microscope, and also the individual observer can obtain different magnifications by either using different accommodations, or by viewing in passive accommodation.