ct 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. I am
now at liberty to state that my photo-electric battery, presently to be
described, marks an advance in the direction indicated. The current from
this battery increases the sensitiveness of the cells to light, and also
to reversal of current. One cell whose highest ratio in light was about
83 to 1, with the Leclanche battery, when measured with my battery gave a
ratio of 120 to 1. It seems to make the resistance of the cell both
higher in dark and lower in sunlight than with the Leclanche battery. But
the field is yet open to others, for the discovery of a battery which may
be still better for use with selenium cells.

3. _The two surfaces of the selenium act differently toward currents_
sent into them from the contiguous conductors. One surface offers a
higher resistance to the current than the other. The former I utilize as
the anode surface, as I have found that the cell is more sensitive to
light when the current enters at that surface, which is ordinarily the
one covered by the gold or other transparent conductor. Some cells have
this property but feebly developed; but in one instance the resistance
offered to the current by the anode surface was 256 times as high as that
offered by the cathode surface to the same current. In the majority of
cases, however, the ratio does not exceed ten times. Table B gives some
recent results.

TABLE B.

SENSITIVENESS TO REVERSAL OF DIRECTION OF CURRENT.

-----------------------+--------------+------------------+---------
| | Resistance |
No. of cell. | Battery. | "gold | "gold | Ratio
| | anode."|cathode."|
------------