2 THE POPULAR SCIENCE MONTHLY. 



shape, not only by diurnal motion, but by the more potent influence 

 arising from the attraction of a great central orb, similar results mav 

 be obtained, but they admit of a more obvious explanation. The ac- 

 companying figure will give an idea of the manner in which, in such 

 dangerous ground, a secondary planet would be affected, especially if it 

 were composed of homogeneous and very yielding materials. If the 

 two bodies were as disproportionate in size as Jupiter and his nearest 

 moon, stability would be impossible on the minor one as soon as gravity 



at the extremities of its longest diameter was reduced more than fifty 

 per cent, by the disturbances. Of the fatal effects of a further reduc- 

 tion adequate proofs are afforded by three different modes of investiga- 

 tion which I have given in the " Philosophical Magazine " for 1860, 1861, 

 and 1871. Accordingly, on coming into fatal proximity with its pri- 

 mary, such a satellite would not lose its matter in small portions, but 

 would pass away in one great convulsion which would destroy the plan- 

 etary condition and give birth to a ring. 



The insecurity which analysis shows in this case in the mundane 

 structure arises from the circumstance that, when gravity is reduced to 

 less than one half its value along the greatest axis, the pressure along 

 that line can no longer be made to counterpoise the pressure from other 



