Between the bridge and the cell is a reversing
switch, so that the current can be reversed through the cell without
changing its course through the bridge. A Bradley tangent galvanometer is
used, employing the coil of 160 ohms resistance. The Leclanche battery is
exclusively used in measurements for comparison.
2. _The kind of battery employed_ has a marked effect upon the
sensitiveness to light, which is largely reduced or entirely destroyed
when the bichromate battery is used. The same cells again become
extremely sensitive with the Leclanche battery. We might expect that a
change in the current employed would cause a change in the _resistance_
of a cell, but it is not clear how or why it should affect the
_sensitiveness of selenium to light_.
"If one kind of battery current destroys its sensitiveness, may we not
suppose that another kind might increase its sensitiveness? Although the
Leclanche has operated well, some other may operate still better, and by
its special fitness for use on selenium cells may intensify their
actions, and so bring to light other properties yet unthought of. Is not
here a promising field for experiment, in testing the various forms of
battery already known, or even devising some new form especially adapted
to the needs and peculiarities of selenium cells?"
One year ago I made the foregoing suggestion in a paper on _A New Form of
Selenium Cell_, presented before this Association at Minneapolis.
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