point out, in a very encouraging manner, the ingenuity or force of
any remarks that were made, when they merited these characters. His
object, as well as Dr. Aikin's, was to engage the students to
examine and decide for themselves, uninfluenced by the sentiments
of any other persons." [2]

It would be difficult to give a better description of a model teacher
than that conveyed in these words.

From his earliest days, Priestley had shown a strong bent towards the
study of nature; and his brother Timothy tells us that the boy put
spiders into bottles, to see how long they would live in the same
air--a curious anticipation of the investigations of his later years.
At Nantwich, where he set up a school, Priestley informs us that he
bought an air pump, an electrical machine, and other instruments, in
the use of which he instructed his scholars. But he does not seem to
have devoted himself seriously to physical science until 1766, when he
had the great good fortune to meet Benjamin Franklin, whose friendship
he ever afterwards enjoyed. Encouraged by Franklin, he wrote a "History
of Electricity," which was published in 1767, and appears to have met
with considerable success.

In the same year, Priestley left Warrington to become the minister of a
congregation at Leeds; and, here, happening to live next door to a
public brewery, as he says,

"I, at first, amused myself with making experiments on the fixed
air which I found ready-made in the process of fermentation. When I
removed from that house I was under the necessity of making fixed
air for myself; and one experiment leading to another, as I have