Andrew Claude de la Cherois Crommelin

“ The meteoric constitution of a comet's head also gives us an explanation of the formation of the tail. We have seen that meteoric lumps contain much gas; on approaching the sun, its heat draws out this gas, which forms a cloud round the comet's head. A violent repulsive force from the sun then acts on the gas, driving it with great speed away from the sun. This force does not disturb the big lumps forming the comet's head, but only the finely divided matter in the tail. A cornet's tail is not attached to it like an animal's tail ”

“ Another very grand comet appeared in 1811, at the time of Napoleon's Russian campaign. This had a tail 100 million miles long, and a very bright head, which was the more remarkable because the comet was outside the earth's orbit, and did not approach close to the sun. It takes some 3,000 years to go round the sun; the periods of some comets are longer still, and they go out into space to some thirty times the distance of Neptune, the furthest known planet. I have estimated that the total number of comets can hardly be less than an eighth of a million. ”

“ The conclusion is that the swarm of meteors that forms a comets head is gradually scattered under the distortion produced by the sun and the planets , so as to leave a long trail of meteoric débris, in the wake of the comet. A meteor shower takes plaice when the earth traverses one of these trails ”