Stable and Unstable Orbits 245 



second to 3 tons, in 3-5 seconds to 2 tons, and in 7 seconds to 

 i ton, while in 13 seconds the pressure is well below that 

 amount. He had corroborated the results by two or three 

 experiments. Powder gases exploded at the same pressure 

 took triple the amount of time, but this perhaps might be 

 expected because of the larger charges fired and the lower 

 temperatures developed. 



June I4th, 424th meeting. Professor G. Darwin stated 

 that, on a recent consideration of the ' three bodies problem,' 

 he had found a possible mode of motion for a satellite, 

 which would give it three changes of moon and one full moon 

 in a single lunation. Its orbit would be a figure of eight 

 relatively to the sun and planet, the latter lying in the larger 

 loop of the eight. Such an orbit is, however, very unstable, 

 so that the satellite, if slightly displaced, must soon cease 

 to move, even approximately, in its primitive orbit, with 

 the result that, sooner or later, it will either come into collision 

 with the planet, or be drawn towards and fall into the sun. 

 Thus all unstable orbits will gradually be eliminated from 

 a solar system, those that are stable alone remaining. By 

 considering the stability or instability of various periodic 

 orbits he was in hopes of throwing light on the actual 

 distribution in space of planets and satellites. 



Professor Victor Horsley gave a brief account of Erlach's 

 experiments with a solution of methylene blue. When this 

 is introduced into the system during life, the colouration 

 or non-colouration of any tissue showed whether oxidation 

 or reduction took place in that part of the body. During 

 life (he had repeated Erlach's experiments on a large scale) 

 no reduction took place in the muscles (including the head) 

 and the brain ; in the lungs the blue was rapidly deoxidized 

 and the tissues remained colourless. At the moment of 

 death the colour instantly fades from tissues, where in the 

 living state it is very pronounced, showing the occurrence 

 of an active and universal reduction. 



Oct. 25th, 425th meeting. The members discussed some 

 subjects in electricity, such as Professor Lenard's observa- 

 tions on cathode rays, the currents about magnetic poles, 



