vi, [8], 603, [1] pp. Illustrated with 26 plates, maps, etc. at rear of volume. (8vo) half leather and marbled boards, raised bands on spine, gilt lettering on spine, gilt top edge, marbled endpapers. First Edition.

Ohm's piece appears on pages 401-506, being the First English Edition of one of the most important works on electricity ever published, representing the discovery of "Ohm's Law", the fundamental law of electrical circuits, namely that E (electromotive force) equals I (current) x R (resistance). By working with wires of different thickness and lengths he Ohm found the quantity of current transmitted was inversely proportional to the length and directly proportional to the cross-sectional area of the wire. He was in this way able to define the resistance of the wire and in 1827 to show that there was a simple relation between the resistance, the electrical potential, and the amount of current carried. This came to be called Ohm's law.