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PHOTO PLATES--WET AND DRY.


Dr. Eder has recently published, in the _Correspondenz_, the first of
a series of articles embodying the results of his more recent work on
gelatino bromide; and we now reproduce the substance of the article in
a somewhat abstracted form.

The "sensitiveness of a wet" plate continues to be used as a rough and
ready standard of comparison; and, notwithstanding the fact that it is
physically impossible to exactly compare the sensitiveness of a wet
plate with that of a gelatino bromide film, it is convenient to refer
to wet plates as some kind of a rough standard.

Experiments have shown that a gelatine plate which gives the number 10
on the Warnerke sensitometer, may be regarded as approximately
corresponding to the average wet plate; and setting out from this
point, the following table has been constructed:

Sensitometer Sensitiveness, expressed in terms
number. of a "Wet Plate."

10 1
11 1-1/3
12 1-3/4