Chase.] ^68 [-jan. 19, 



The seven loci which represent harmonies of nucleation, condensation 

 and nebulosity, illustrate the tendency of waves in elastic media to main- 

 tain and propagate motions which are harmonically dependent upon their 

 loci of origination. 



306. Velocity of Incandescence. 



Draper found that all solid bodies become incandescent at the same 

 temperature, reaching red heat at 977^ F., or at the absolute temper- 

 ature of 1436^.4 F. This indicates a lift, against earth's superficial 

 gravitation, of A = 1436.4 X 772 = 1,108,901, or a velocity of ?) = y/^ 

 = 8435.9 feet per second. The mean velocity of hydrogen molecules is 

 6050 feet, which is .717 X 8435.9 feet. The velocity of incandescence is. 

 therefore, within 1^ per cent, of the parabolic orbital velocity which would 

 correspond to a circular orbital velocity equivalent to the molecular 

 velocity of hydrogen, (6050 X v/3 = 8556). In other words, if the mean 

 velocity of hydrogen, at the standard temperature, is a mean orbital 

 velocity, its increase to a velocity of infinite projection would give the 

 velocity of incandescence, or the velocity which creates sethereal disturb- 

 ances of sufficient magnitude to cause luminous radiations. These dis- 

 turbances are of the same order of magnitude as those which are indicated 

 in Note 304, and they furnish new reasons for believing that the hypoth- 

 eses ot Siemens and Berthelot (Note 278) may suffice to account for the 

 conservation of energy which is indicated by the fundamental equality, 

 »^=ii^=,„^, (Note 280). 



307. Tails of Comets. 



Proctor (Contemp. Eev., Oct. 1882) states some of the chief difficulties 

 attending the attempts which have been made to explain the formation of 

 comets' tails, by materials thrown off from the nucleus by solar repulsion, 

 by actinic clouds, by tactic arrangement, or by electricity, and speaks of 

 certain phenomena "which force upon us the belief that they are phe- 

 nomena of repulsion, though the repulsive action is of a kind not yet 

 known to physicists." He inclines, with Huggins, and "an American 

 astronomer" whose name is not given, to attach great importance to 

 electric action or something of a similar nature. He cites the notice by 

 Huggins, of the remarkable persistence of meteoric trains in the rare 

 upper atmosphere, where they sometimes last for more than three-quarters 

 of an hour. The evidences of repellent action such as might be explained 

 by electricity, of gravitating re-action, of luminous radiation from the sun 

 in the dli-ection of the axis of the tail, and of a general curvature of the 

 extremity of the tail as if it were retarded in some way, are such as to 

 need consideration in any attempts at explanation. All of these phenom- 

 ena, except the one last named, may be correlated by the fundamental 

 equality of Note 280. The curvature of the tails may be due to persistence 

 of oscillation, combined with a^thercal tendencies to orbital motion in 

 times varying as r|. The extreme tenuity of coiuetary matter points to a 



