166 Transactions. — Miscellaneous. 



by having the oscillations of one small and the other large. By hanging 

 two balls of equal volume and different mass, the oscillations of the lighter 

 will be destroyed much quicker than those of the heavier one ; thus illus- 

 trating the greater power to do work possessed by the heavy body, as the 

 resistance of the air is the same in both cases. 



A large number of experiments of resultant motion may be proved by 

 first showing the isocranism of all lengths of vibrations, and then striking 

 the moving pendulum when at its several points of motion. These form a 

 most instructive series of experiments. The conversion of circular into 

 straight, and straight into circular, elliptical, and diagonal motion, is of 

 course very easily illustrated. 



As is well known, the peculiarities of kinetic and potential energy are 

 better shown to a class by a pendulum, than probably by any other method. 



Akt. XVII. — Prohahility of Impact. By Professor A. W. Bickekton. 

 [Read before the Philosophical Institute of Canterbury, 4th November, 1880.] 

 The remarks made by several members show that the general statement 

 as to the improbability of steUar impact which Proctor made in his lecture, 

 but which was specially directed against Croll's theory of the origin of the 

 sun's heat, are taken also to include tangential impacts. I entirely agree 

 with Proctor in his opinion of Croll's hypothesis, and in 1878 I wrote a letter 

 to "Nature," showing it to be in the highest degree improbable. It requires 

 the stupendously unlikely event that two equal bodies, when at the limits of 

 effective attraction, are directly approaching each other with a velocity of 

 250 miles a second. Those who have followed the reasoning in connec- 

 tion with "Partial Impact," must see how amazing is the gulf that sepa- 

 rates the two suggestions. 



Even if such an impact as Croll suggests were probable, such an event 

 would not assist in removing the difBiculty of the age of the sun's heat, 

 for in my paper on " The Origin of Nebulae," I have shown that a nebula 

 must be dissipated into space if it possesses more energy than that pos- 

 sessed by infinitely diffused gaseous matter. Therefore, if at impact the 

 sun received so much heat that it made a nebula hotter than would be the 

 case if it had condensed from diffused gas, then such a nebula would tend 

 to dissipate rather than condense. On the contrary the hypothesis given 

 by Proctor, that the sun is highly condensed in the centre, affords so satis- 

 factory an explanation to me, that when I read the article suggesting this 

 theory I at once accepted it. It is also evident to any one who understands 



