| 1 | After switching on powerful arc lights. | |
| 2 | Outside the arc-light shone through the bare branches of a tree. | |
| 3 | If the arc lamps are almost new, proceed as follows. | |
| 4 | After switching on powerful arc lights, they saw great stalagmites. | |
| 5 | No colour fade after 300 hours close distant exposure to arc lamps. |
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