OP ARTS AND SCIENCES. 203 



tion was illustrated by diagrams, in which the observations were all 

 combined into three tails, which may be designated as normal tails, 

 and of which the dates were respectively the second, the ninth, and 

 the fifteenth of October. 



" 5. An attempt was next made to satisfy the observations by a 

 sensible initial velocity arising from the action of the comet's nucleus, 

 and in which there should be neither repulsive nor attractive force 

 exerted upon the particles of the tail. But it was found impossible to 

 accomplish this result. 



" 6. It was found equally impossible to satisfy the observations by 

 Pape's theory, in which the solar force is supposed to be attractive, 

 or slightly repulsive ; and the difference between this result and that 

 obtained by Pape must be attributed to the defects of the approxi- 

 mative formulae envployed by Pape. It may otherwise be regarded 

 as objectionable to Pape's theory, that it assumes the solar force to be 

 so variable in its action, and the initial velocity arising from the action 

 of the comet's head to be so large. 



" 7. In the present theory, however, the solar force is not found to 

 be constant for all the particles of the tail, but to vary from the 

 extreme repulsion = — 1^ down to zero, or even to be attractive for 

 the particles upon the back edge. But the back edge is so badly 

 defined, that the observations upon it cannot contribute much to the 

 accuracy of these investigations. 



" 8. The streaks of light, which were observed about the time of 

 greatest brilliancy, towards the extremity of the tail, are probably to 

 be attributed to the continuous discharge of material from different 

 points of the nucleus. It was an amusing and juvenile play of fancy 

 which saw in this phenomenon indications of concentration into new 

 comets. 



" 9. The suggestion that the dark line in the tail, near the head, 

 may be shadow, is quite absurd. The shadow of so small a nucleus 

 could not have been in the least degree perceptible to us, and the 

 accurate measures which were taken, as they should have been, by the 

 most competent observers, show that the direction of this dark line 

 sensibly deviated from that of the radius-vector from the sun, which 

 must have been the direction of li shadow. A diverging shadow in 

 this case is too preposterous for argument. The darkness can only 

 be explained by an actual deficiency of the matter of the tail, and 



