Electrical machine

This cylindrical electrical machine was made around 1785, probably in London. Although not as popular as the contemporary disc friction electrical generator, the cylindrical form was put to medical use, encouraged by the instrument maker Edward Nairne of London. This particular example was purchased by the Royal Medical Society, a student society of the University of Edinburgh, in London, around 1785.

This Nairne-type machine can obtain both positive and negative charges of equal magnitude, as the cylindrical brass conductors are of equal surface area on either side of the glass cylinder and insulated on glass supports. These can slide backwards and forwards and are secured with ivory thumb-screws. The glass cylinder is turned by a wooden crank.

The first cylinder machine was probably designed in Germany in the middle years of the 18th century. Many modifications and improvements in detail were made during the next 25 years. Edward Nairne took out a patent in 1782 for his 'insulated medical electrical machine', of which this appears to be an unsigned example.

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