Fig. 14.—Showing needle laid in position across pins.
If a small paper dial be made against the pointer, the amount of the expansion can be even more clearly observed. Of course two or even more candles may be used, the result being that the needle shows more and more expansion as it becomes hotter.
The Broken Bottle
An interesting and useful experiment with a broken bottle is depicted in [Fig. 15].
Fill the broken piece with oil to whatever level you desire it to be cut, and stand it upon a perfectly level table. Now plunge a red-hot poker into the oil and hold it there for a few seconds, when there will be a loud crack, and the top of the broken part will come off, even and smooth, as in [Fig. 16].
Fig. 15.—Portion of broken bottle for experiment.
Fig. 16.—Showing smooth break after red-hot poker has been plunged into the oil.
It may not be generally known that a sheet of glass may be cut regularly and evenly with a pair of strong scissors.