Excerpt from Weston Monographs: Combined Under One Cover for the Convenience of Science Teachers in High Schools and Collegiate Preparatory Schools
Otto von Guericke, about the year 1640, constructed an electrical machine consisting of a ball of sulphur mounted upon a shaft, and revolved by means of a crank. The ball was electrified by friction against the hands of one of the operators. About 1670 Newton repeated these tests, substituting a glass globe. In 1705 Hawksbee produced a machine similar to Newton's.
Electrical machines were also made with glass cylinders and glass plates instead of spheres, and it soon became apparent that the size of the cylinder or plate, as well as the speed at which it was revolved, had something to do with the length of the spark, and the quantity of electricity obtained. And it was also noted, even if somewhat vaguely, that there was some relation between the amount of power applied and the electricity obtained, and that the big machines gave more impressive results than the little ones, at least from a spectacular standpoint. Of course, for exhibition purposes, larger and still larger machines were constructed. Probably the most enormous contrivance of this kind was displayed at the Panopticon in London, nearly a century ago.
This machine was designed by Mr. Warner, and was over twenty feet in height. Its revolving glass plate was ten feet in diameter. Under favorable conditions it gave a spark over two feet in length.
Incidentally, it is a little difficult to decide why a real or imitation tortoise was used to support the large insulator and prime collector.
Numerous types of static machine were invented in addition to these, many of which were more efficient than Warner's, although much smaller in size. In fact a machine, which depends upon induction instead of friction, invented by Holtz of Berlin in 1865, gives a spark the length of which is over half of the diameter of its revolving plate.
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