ABSTRACT
In the post-Newton era, two other forms of energy of a more mysterious kind were being studied, electricity and magnetism. Early in the next century, its significance was to reach mammoth proportions and it would become a part of the greatest revolution natural philosophy had experienced since Isaac Newton. The very end of the nineteenth century, it seemed that the natural philosophy initiated by Newton, to be called classical physics, had almost completed its task. The discovery of Neptune was one of the many great triumphs of Newton’s theory of gravitation, but it is appropriate to mention that there was another planet which displayed a very small deviation from a purely Newtonian orbit which could not be explained at that time in the nineteenth century. Like the non-Newtonian but different perturbations in the orbit of Uranus, the effect in Mercury was ascribed to another planet which would have to lie inside its orbit and closer to the Sun.
