BiCKERTON. — On the General Problem of Stellar Collision. 181 



6. The most casual study of " partial impact " shows that for a long 

 time after impact, at least, streams and sprays of fragments must exist, and 

 also that there should be considerable community of motion. Proctor has 

 demonstrated this to be the case. 



7. Original rotation of mass would tend to take material slightly out of 

 the ecliptic as streams. Original orbital rotation of smaller bodies would 

 tend still more to take these bodies out of the general plane, but more 

 irregularly. This appears to explain much of the definite irregularity of 

 the visible universe. 



Besides these general agreements, all the minor observations I have 

 mentioned seem to point quite to the same conclusion. How like a con- 

 tinuance of the original motion does the clustering of the stars at opposite 

 points in the ring appear. 



The varied motion in the plane of the ring must produce many collisions,, 

 resulting in temporary and variable stars, and nearly every one of these is 

 in this plane. Nebulae of definite structure, such as planetary and annular, 

 probably originate in the same way, at least partial coUision offers a perfectly 

 intelligible account of them, and I know of no other that does. These are 

 also in the same small area in the heavens. 



Speculation concerning the origin of the hollows in the milky way, also 

 in the milky-way nebulse, and relating to these bodies themselves, as well 

 as the Magellanic clouds, so also discussions relating to the available energy, 

 the cause of the extinction of light and of the stability of the cosmogony, 

 although belonging to this subject, must be left to future papers. 



I cannot conclude the brief account of this wonderful and beautiful 

 galaxy, of which our earth forms so minute a portion, without hoping that 

 it may induce others to enter this fascinating and extensive field of research ; 

 — workers whose time and skill in observing, and whose higher mathemati- 

 cal training may enable them to deal exhaustively with some of the many 

 and original difficult problems which this view of the universe suggests. 



Art. XIV. — Partial Impact (Paper No. 4) : On the General Problem of Stellar 

 Collision. By Prof. A. W. Bickerton, F.C.S., President of the Philoso- 

 phical Institute of Canterbury. 



Plate VI. 



[Read before the Philosophical Institute of Canterbury, 27th Februai-y, 1879.] 



The papers I have presented to the Institute on the possible phenomena 

 connected with the partial coUision of cosmical bodies, show that this 

 variety of impact is deserving of very careful study. I shall, therefore, in 



