Electricity, as a field of experimental science, grew out of Gilbert's monumental treatise on the magnet ( 1600), and von Guericke's description of the (static) electrical machine ( 1672). Von Guericke's machine, a sulphur globe turned by a crank and electrified by turning against the hand, was the prototype of a variety of machines invented in the following century. By the middle eighteenth century many experimenters were occupied with electricity and a considerable literature existed. Because of the spectacular character of its manifestations, it had become a favorite subject with popular lecturers on science.
In 1743 or 1744 one of these lecturers, a Dr. Adam Spencer, seems to have been the source of Franklin's first contact with the subject. The most important piece of apparatus at this time was a glass tube which, when rubbed, constituted the "machine" for the production of the "electric fluid." Such tubes were apparently more common among "electricians" than the more expensive and cumbersome apparatus deriving from von Guericke's globe. A tube was presented to the Library Company by Peter Collinson in 1746, and was used by the Philadelphia experimenters in their early investigations. The demand of Philadelphians for electrical experiments was such that Franklin directed the manufacture of tubes in the local "glass house." One of the present specimens (58-38, fig. 9) may represent the product of this enterprise.
The Philadelphians were apparently not acquainted with machines of the type of von Guericke. Philip Syng, one of Franklin's fellow electricians, reinvented it using a glass globe, and these too were made at the glass house. This may also be represented in the present collection (58-37). The plate machine, developed in Europe shortly after this time, is represented (58-39), as is the most important piece of accessory equipment, the Leyden jar. This device was invented or discovered in Europe in 1745- 1746, providing not only the first convenient reservoir for the storage of static electricity, but a vehicle for much of Franklin's work. He contributed greatly to the elucidation of the Leyden