166 FROM NEBULA TO NEBULA 



tional origin) soon finds itself so far away from strong 

 rival attractions that it is able to make its integral at- 

 traction among its scattered parts dominantly felt, and, 

 eventually, though its aggregate mass be slight, to con- 

 solidate them into a single ball, or perhaps into a vorti- 

 cal swirl, or gravitational unit, of small diameter. After 

 entering the sphere of the sun's influence and connect- 

 ing up with its predestined orbit, as it were, the comet 

 forges on in regular course to its perihelion. Had it now 

 nothing but its projectile momentum to depend upon, it 

 would lose so much of this in "turning the corner " that 

 it would inevitably fall in upon the sun. But, thanks to 

 the torsional force of the quiver of rays of attraction that 

 make up the Prime Eesultant, the comet is upheld 

 against the straining sun and whisked past his eager 

 grasp, thwarting that Tantalus of his expected feast. 



The crisis, however, has not been without its serious 

 effects. The fierce heat from the luminary falling upon 

 the massed particles, though perhaps not intense enough 

 to fuse, their crusts, is certainly able to raise their gen- 

 eral temperature to a high state, thereby causing expan- 

 sion of the confined gases, and so giving rise to multi- 

 tudinous explosions of every degree of intensity. These 

 phenomena, in the very nature of things, are most pro- 

 nounced when a comet is very near the sun; which is 

 unfortunate for human observation, because of the blind- 

 ing contrast of the solar rays. The effects, however, are 

 sometimes sufficiently pronounced to be seen and studied 

 even despite this handicap, and reveal themselves in 

 such strange phenomena as glowing nuclei, jets, enve- 

 lopes, coma, and tails. 



COMETARY PHENOMENA EXPLAINED 



In nearing the sun, the integral attraction of the 

 comet becomes dwarfed in competition with the rapidly 

 augmenting solar attraction and a new disposition of its 

 component substances is rendered imperative. Instead 

 of preserving its old sphericity, therefore, it tends to 

 the columnar form, with its heavier elements at the base 



