( hapman. — Notes on a Meteoric Appearance. 143 



mass to be moved, the temperature would rise enormously 

 beyond what it would ultimately be on the establishment of an 

 equilibrium. Hence it is quite in accordance with what we 

 ought to expect if. on a collision between two bodies, the tempera- 

 ture should rise in a few hours or days so greatly that the joint 

 mass would shine as a bright star. But this state of things 

 could not be permanent, as the gravity of the mass would be 

 insufficient to counteract the expansive force created by the 

 enormous accession of heat. The mass would therefore expand, 

 the rate of expansion being slow at first, increasing to a maxi- 

 mum, and finally dying out. The body would then be enor- 

 mously diffused, but at a moderate temperature. The greater 

 the velocity of the impact the lower would be the final tem- 

 perature. A velocity can be assigned at which the body would 

 be dissipated in infinite space, and the temperature exactly 

 zero ; but this velocity could nob be acquired by the mutual 

 attraction of the colliding bodies. With any velocity which we 

 can admit as probable the final state of the mass would be a 

 globe vast in proportion to the sum of the original volumes of 

 the colliding bodies, with a moderate temperature. Such a bodv 

 would present the appearance of a planetary nebula. 



Before this final stage was reached there would be fluctuations. 

 The outward velocity communicated to the gaseous atoms 

 would cause the first expansion to go beyond equilibrium ; in- 

 deed, the outward velocity at. the position of equilibrium would 

 be a maximum. Hence the body would be overexpanded 

 and overcooled. It would then condense again, with a rise in 

 temperature again overcompensated. This might, indeed would, 

 be repeated many times, finally dying out. These pulsations 

 appear to have been observed. 



The consideration applied here to two colliding globes would 

 equally apply to colliding flights of meteors, but the effects 

 might not be so marked — the rise in temperature would be more 

 gradual. They would also apply to the case of a sphere plung- 

 ing into a vast hydrogen region, such as the spectroscope re- 

 veals to us. 



Art. XXIV. — Notes on a Meteoric Appearance. 

 By Martin Chapman. 



[Read before the Wellington Philosophical Society, 2nd August, 1905.] J 



I think it as well to put on record a remarkable phenomenon 

 which was observed by myself, with many others, on thy even- 

 ing of the 9th June. A party of us left Otaki by the evening 



