The attention of Dr. Priestley, the discoverer of so many gases, was accidentally drawn to the subject of chemistry through his living in the neighbourhood of a brewery. When visiting the place one day, he noted the peculiar appearances attending the extinction of lighted chips in the gas floating over the fermented liquor. He was forty years old at the time, and knew nothing of chemistry. He consulted books to ascertain the cause, but they told him little, for as yet nothing was known on the subject. Then he began to experiment, with some rude apparatus of his own contrivance. The curious results of his first experiments led to others, which in his hands shortly became the science of pneumatic chemistry. About the same time, Scheele was obscurely working in the same direction in a remote Swedish village; and he discovered several new gases, with no more effective apparatus at his command than a few apothecaries’ phials and pigs’ bladders. Sir Humphry Davy, when an apothecary’s apprentice, performed his first experiments with instruments of the rudest description. He extemporised the greater part of them himself, out of the motley materials which chance threw in his way,—the pots and pans of the kitchen, and the phials and vessels of his master’s surgery. It happened that a French ship was wrecked off the Land’s End, and the surgeon escaped, bearing with him his case of instruments, amongst which was an old-fashioned glyster apparatus; this article he presented to Davy, with whom he had become acquainted. The apothecary’s apprentice received it with great exultation, and forthwith employed it as a part of a pneumatic apparatus which he contrived, afterwards using it to perform the duties of an air-pump in one of his experiments on the nature and sources of heat.