In 1820, while lecturing before his class, he became convinced that the apparatus he was then using could be made to demonstrate the correctness of his views. He asked his pupils to accompany him to his laboratory, where, as he predicted, a slight deflection of the magnetic needle, turned at right angles to the electric current, was shown when placed close to the copper wire. Some months afterwards, with a stronger current (made up of twenty cells), he obtained much more intense effects. Investigating these in detail, he found that they met all the requirements of his theory. So, on July 21, 1820, he sent out to the scientific world his now famous circular, “_Experimenta circa effectum conflictus electrici in acum magneticum_” (Experiments on the effect of the electrical conflict in the magnetic needle). Örsted showed, furthermore, how changes in the position of the magnetic needle occurred with variation of the position of the conductor (copper wire) in regard to it. He demonstrated also that the magnetic effect was not weakened by insulators—that it would penetrate various materials, whether these were conductors of electric currents or not. He showed that the magnetic field created by the electric current does not have any influence on a needle of non-magnetic material—i. e., brass, glass, etc. It is, in fact, chiefly in the fact that it cannot be insulated that magnetism differs from electricity. It will freely pass through air, stone, mica, glass, clay, brick, or any insulating material. It is well worthy of especial mention that Örsted employed the term “_conflictus_” to designate the electric current, many decades before the origin of the electron theory of matter. For, on modern theories of electricity, it is the movement to and fro of electric particles (electrons) through the conductor, and their impact (“_conflictus_”) that produces what we call electrical phenomena. Örsted’s fundamental discovery of the mutual effects between electricity and magnetism led to further discoveries which made possible the construction of telegraph and telephone instruments, since these depend on the fact that _an electric current can produce magnetism, and that magnetism can produce an electric current_.