resides in it contributed from all the other parts, just as all the soldiers bring help to their own commander. Wherefore also a slightly longer stone attracts more than a spherical one, since the length from pole to pole is extended, even if the stones are both from the same mine and of the same weight and size. The way from pole to pole is longer in a longer stone, and the forces brought together from other parts are not so scattered as in a round magnet and terrella, and in a narrow one they agree more and are better united, and a united stronger force excels and is preeminent. A much weaker office, however, does a plane or oblong stone perform, when the length is extended according to the leading of the parallels, and the pole stops neither on the apex nor in the circle and orbe, but is spread over the flat. Wherefore also it invites a friend wretchedly, and feebly retains him, so that it is esteemed as one of an abject and contemptible class, according to its less apt and less suitable figure. * * * * * {83} CHAP. XV. * The Magnetick Virtue which is conceived in Iron is more apparent in an iron rod than in a piece of iron that _is round, square, or of other figure_. Duly was it said before that the longer magnet attracts the greater weight of iron[167]; so also in a longish piece of iron which has been touched the magnetick force conceived is stronger when the poles exist at the ends. For the magnetick forces which are driven from the whole in every part into the poles are not scattered but united in the narrow ends. In square and other angular figures the influence is dissipated, and does not proceed in straight lines or in convenient arcs. Suppose also an iron globe have the shape of the earth, yet for the same reasons it drags magnetick substances less; wherefore a small iron sphere, when excited, draws another piece of iron more sluggishly than an excited rod of equal weight. * * * * * CHAP. XVI. Showing that Movements take place by the Magnetical Vigour though solid bodies lie between; and on _the interposition of iron plates_.