16 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



law of repulsion of incandescent surfaces. He considers that 

 white-hot bodies in general exert a repulsive force on matter 

 in a very rarefied state, but that this force differs from that of 

 gravitation in residing in and acting upon the surfaces of bod- 

 ies only, and in being intercepted by a screen of solid matter. 



Considering the existence of this apparent repulsive force 

 as indisputable, M. Faye passes in review the theories of its 

 origin. First, we have the theory of Newton, now forgotten 

 in England, that the sun is surrounded by an extremely rare 

 atmosphere extending beyond the orbit of the earth, and that 

 the rare matter of the comet's tail rises in this atmosphere, 

 just as smoke does in our own atmosphere. The objection 

 to this theory is that the sun is not and can not be surround- 

 ed by any such atmosphere. 



Then we have the hypothesis of Olbers, now adopted by 

 Zollner, that the repulsion is due to the electricity of the 

 sun. This last investigator shows that if the electric tension 

 of the outer layers of the sun's atmosphere is as great as is 

 frequently seen at the surface of the earth, a little sphere of 

 matter, half an inch in diameter, and weighing one sixtieth 

 of a grain, repelled by the supposed electricity of the sun's 

 atmosphere, would, when it reached the orbit- of Mercury, be 

 flying with a velocity of 2000 miles- per second. This view 

 is objected to because it is shown that there can be no elec- 

 tric action in a vacuum. 



Another theory lately put forward is that of Professor Tait, 

 who, however, dispenses with the repulsive force, and consid- 

 ers that the whole comet is only a vast swarm of flying me- 

 teorites moving in a flat layer, which is only visible when 

 we look at it edgewise. He compares it to a flock of birds, 

 which are invisible when spread out, but plainly seen when 

 they are in a line with the eye of the observer. M. Faye 

 considers that this theory sets at naught all existing science, 

 whether observations or theory. But he looks with more 

 favor on another part of Tait's theory that the light of the 

 comet arises from collisions anions the meteorites which com- 

 pose it, and which are thus continually striking fire, as we 

 may familiarly express it. 



M. Faye has attempted to prove his hypothesis by trying 

 whether a white-hot metallic plate would repel rarefied air. 

 The experiment was made in the presence of several savants, 



