h of the simplest
construction until the third paper. In the second paper, meanwhile, he
had illustrated two peculiar designs involving the principle in less
elementary ways.

His indifference to whether the wire loops lie _in_ the magnetic
meridian (fig. 3) or perpendicular to it (fig. 5) or "at any other
arbitrary angle to it," reveals a poor appreciation of the
measuring-instrument potentialities. His conception seems to be
primarily that of a detector.

Poggendorf's invention, as first reported by Erman and presented to a
wider audience by Gilbert[26] was described as consisting of typically
40 to 50 turns of 1/10-line diameter, silk-covered copper wire tied
tightly together, with the whole pressed laterally to form an elliptical
opening in which a pivoted compass needle could move freely while
maintaining clearance of about 2 lines from the wire at all points.[27]

"This magnetic condenser can be a great boon to electro-chemistry," said
Erman, for "it avoids all the difficulties of electric condensers." He
noted that, using the condenser, Poggendorf had already established the
electric series for a great number of bodies, discovered various
anomalies about conductivities, and found a way of detecting dissymmetry
of the poles of a compass needle. On the other hand, even with the
condenser, no magnetic effects have so far been obtainable from a strong
tourmaline, or from a 12,000-pair, Zamboni dry cell.

Poggendorf's own account of his work finally appeared as a very long
article in the journal known as "Oken's Isis."[28] The editorial
controversies mentioned earlier may have occasioned this use of a
periodical of such minor status in the fields of physics and chemistry.

The source of Poggendorf's vision of the multiplier principle was a
little different from Schweigger's inspiration. Aiming at some detailed
analysis of Oersted's observation, Poggendorf ran the connecting wire of
his cell-circuit along a vertical line to just above or below the
pivot-point of the compass needle, then, after a right-angle bend,
horizontally above or below one of the poles of the needle. As he
studied the deflections produced for all four possible positions of such
a wire, with both cell polarities, he came to realize that if a
rectangular wire loop in a vertical plane enclosed a compass needle, all
parts of the horizontal sides of the loop would produce additive
deflections. By a separate experiment, he showed that the vertical