In other words, to put it plainly and tersely, each aetherial atmosphere revolves round the planet, subject to certain limitations, in the same way that the aerial atmosphere turns round with the earth, as that planet revolves on its axis. At first sight, such an assumption may seem impossible, but a little careful consideration will show not only the possibility of such a cause, but will establish it, as the only reasonable and philosophical explanation for the phenomena we are seeking to explain, viz. the electro-magnetism of all celestial bodies. There is nothing extravagant in this assumption, as we already have a similar illustration in the case of the atmosphere which goes round with the earth as it revolves on its axis. We have only to extend the same principle a little further, viz. to the aetherial atmosphere, and we at once get the true physical conception of the hypothesis suggested to explain the magnetism of all celestial bodies. We have already learned that Maxwell has proved that the equations for moving magnetic bodies are the same as those for stationary bodies, from which we came to the conclusion that the electric and magnetic field of any planet goes with that planet as it revolves on its axis in its journey round the sun. I would like to ask the reader to try to conceive of any electric or magnetic field traversing space in association with any planet or sun which is revolving on its axis, while that electric or magnetic field does not revolve either partially or wholly with the revolving body. The field can only be stationary relatively to the planet or sun, as it revolves with the planet or sun on its axis. There may be, as there doubtless are, conditions governing that revolution, as is the case with the atmosphere moving and revolving with the planet, but it is an absolute impossibility for Maxwell's equations relating to moving magnetic bodies to be carried to their logical conclusion, without affirming some such hypothesis as we have affirmed in relation to the cause of all solar magnetism.