be made
accordingly.

In looking over the magazines and annuals we will now and then see some
new method given for illuminating evenly the back of a negative in
enlarging or reduction. The most of these the writer has tried, but he has
never found one of them which could be relied upon to give even reasonable
satisfaction. If the light is apparently evenly diffused it is too weak.
If strong enough it is not evenly diffused. Hence I will recommend nothing
short of a pair of condensing lenses, as these have been proved by
experience to be satisfactory in every respect if properly handled and
cared for. The diameter of these must be slightly greater than the
diagonal of the largest negative from which enlargements are to be made.
These can be bought in pairs, mounted or unmounted, at about the following
prices:

---------+-----------------+----------------+------------------
Diameter | Focus | Pair of Lenses | Per Single Lens
Inches | Inches | Mounted | Unmounted
---------+-----------------+----------------+------------------
4 | 5-1/2 or 6-1/2 | $ 4.00 | $ 1.25
4-1/2 | 5-1/2 or 6-1/2 | 6.00 | 1.50
5 | 6-1/2 | 7.50 | 1.75
6 | 8 | 12.00 | 3.00
8 | 12 | 32.00 | 7.50
9 | 14 | 40.00 | 10.00
---------+-----------------+----------------+------------------

The prices asked for condensers vary considerably in different
price-lists. They can often be had at second-hand at a decided saving of
expense.

If it is desired to save the additional cost of the mounted condensing
lenses, they can be comparatively easily mounted by anyone at all familiar
with tools in the following manner:

A piece of quarter-inch pine or poplar is cut to a square about an inch
larger than the diameter of the lenses. In the center of this is sawed out
a circular opening the exact size of the lens. In another board of the
same dimensions is cut a circle a quarter of an inch less in diameter.
These boards are placed together with the grain running in opposite
directions, to prevent warping, and the lens kept in place by a wire bent
in a circle and clamped in place so as to hold the lens, or other similar
arrangement. See Fig. 8. The other lens is mounted in the same way. The
two are mounted with their convex sides facing each other and a slight