These changes of resistance are not due to heating of the conductor or the selenium, and the following instance will illustrate this.  I have one cell in which the selenium has about one-fourth inch square of surface melted on a brass block one inch thick.  This cell measured, with 25 elements of Leclanche, 40,000 ohms.  On changing the battery to 5 elements the resistance fell instantly to 30 ohms, and there remained.  On again using the current from 25 elements, the resistance instantly returned to 40,000 ohms.  Had these results been due in any degree to heating, the resistance would have changed gradually as the heat became communicated to the brass, whereas no such change occurred, the resistances being absolutely steady.  Moreover, even the fusion of the selenium would not produce any such change.

The “U B” property does not ordinarily change the resistance of the cell to exceed ten times, i.e., the resistance with a weak current will not be over ten times as high as with a strong one.  But I have developed the “L B” property to a far higher degree.  Table C gives some recent results obtained with L B cells, including one whose resistance, with 25 elements Leclanche, was 11,381 times as high as with 8 elements, and which, after standing steadily at 123 ohms (and then at 325 ohms with 1 element), on receiving the current from 25 elements again returned to its previous figure of 1,400,000 ohms.

TABLE C.

SENSITIVENESS TO CHANGE OF BATTERY POWER.
-----------------------+------------+------------+----------

---
| Resistance | Resistance |
No. of cell.    |   with 25  |   with 5   |  Ratio of
|  elements. |  elements. |   Change.
-----------------------+------------+------------+----------

---
|  ohms.     |  ohms.     |
3/8 inch square, No. 1 |    40,000  |     30     |  1,333 to 1
3/8  "     "      "  2 |    13,000  |     40     |    325  "
1/4  "     "      "  1 | 1,400,000  |    123[8]  | 11,381  "
1/2  "     "      "  2 |   500,000  |     62     |  8,064  "
1/2  "     "      "  5 |     3,500  |     21     |    167  "
Full size, No. 81   |    68,000  |    121     |    561  "
"    "     "  82   |     9,000  |     64     |    140  "
"    "     "  83   |    17,300  |     74     |    233  "
"    "     " 119   |    35,600  |     19     |  1,894  "
-----------------------+------------+------------+----------

---

[Footnote 8:  This measurement was obtained with 8 elements.]

The results in the table were obtained by changing the strength of current by throwing in more or less of the battery.  Like results can be obtained by varying the current through the cell by any of the other methods before specified.  The above measurements were in dark.