absolutely free from any smack of soot.

[Illustration]

The sketch explains itself. The weight, W, and the angle of the lever,
L, are such, that when the valve, V, is once opened it goes full open. A
small hole in the can C, acts like a cataract, and brings matters to a
normal state very soon after the rain ceases.

The proper action of the apparatus can only be insured by a careful
adjustment of the weight, W, the angle through which the valve opens,
and the magnitude of the vessel, C. It is an advantage to make
the vessel, C, somewhat broader in proportion to its height than
represented, and to provide it with a movable strainer placed about half
way down. This tends to protect the cataract hole, and any accumulation
of leaves and dirt can be removed once in six months or so. Clean soft
water is valuable to the photographer in very many cases. Iron developer
(wet plate) free from chlorides will ordinarily remain effective on the
plate much longer than when chlorides are present, and the pyrogallic
solution for dry-plate work will keep good for along time if made with
soft water, while the lime which is present in hard water causes the
pyrogallic acid to oxidize with considerable rapidity. Negatives that
have been developed with oxalate developer often become covered with a
very unsightly veil of calcium oxalate when rinsed with hard water, and
something of a similar character occasionally occurs in the case of
silver prints which are transferred directly from the exposure frame to
impure water.

To the carbon printer clean rain-water is of considerable value, as he
can develop much more rapidly with soft water than with hard water;