Question

How priestly lightened the candle without touching the belljar

Answer 1

In 1771 and 1772, Joseph Priestley performed a series of experiments that revealed the essential role of air in the growth of green plants.
Priestley observed that a candle burning in a closed space such as a bell jar, soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space.
It was known that a candle placed in a sealed bell jar would eventually burn out and could not be relighted while still in the jar.
In August 1771, Joseph Priestley, placed a mint plant into a transparent closed space with a candle that burned out the air until it soon went out.
After 27 days, he relit the extinguished candle again. Since there was no bright source of light available that time, Priestly had to rely on the sun. He focused sunlight beams with a mirror onto the candle wick and was successful in relighting the candle from outside the bell jar without disturbing the experimental set up.
Now, we can use more sophisticated methods to light the candle like focusing light from a flood light through converging lens, or by an electrical spark.
Priestly discovered that the relit candle burned perfectly well in the air that previously would not support it.