Passages from the Life of a Philosopher

The problem of the three bodies, which has cost such unwearied labour to so many of the highest intellects of this and the past age, is simple compared with another which is opening upon us. We now possess a very extensive series of well-recorded ob­ser­va­tions of the positions of the magnetic needle, in various parts of our globe, during about thirty years. 〈CAUSES OF MAGNETIC CHANGES.〉 Certain periods of changes of about ten or eleven years are said to be indicated as connected with changes in the amount of solar spots; but the inductive evidence scarcely rests upon three periods, and it seems more probable that these effects arise from some common cause. (1.) It has been long known that the earth has at least two if not more magnetic poles. (2.) It is probable, therefore, that the sun and moon also have several magnetic poles. (3.) In 1826 I proved that when a magnet is brought into proximity to a piece of matter capable of becoming magnetic, the magnetism communicated by it requires time for its full development in the body magnetized. Also that when the influence of the magnet is removed, the magnetized body requires time to regain its former state. {472} This being the case, it is required, having assumed certain positions for the poles of these various magnetic bodies, to calculate their reciprocal influences in changing the positions of those poles on the other bodies. The development of the equations representing these forces will indicate cycles which really belong to the nature of the subject. The comparisons of a long series of ob­ser­va­tions with recorded facts will ultimately enable us to determine both the number and position of those poles upon each body. 〈ELECTRIC CHANGES.〉 Electricity possesses an analogous property with respect to time being required for its full action. If the bodies of our system influence each other electrically, other developments will be required and other cycles discovered. When the equations resulting from the actions of these causes are formed, and means of developing them arranged, the whole of the rest of the work comes under the domain of machinery.