Page:A Voyage in Space (1913).djvu/56

36 us once, went away and never came back at all. But soon after Newton's discovery about the law of Gravity, Halley thought he would calculate the orbits of these comets. Perhaps you have not seen a big comet, such as that which appeared in 1858.

A "comet" means a hairy star, and in old days comets were represented as stars with hair. Nowadays we get photographs of them. Anybody who has got a Kodak and can strap it to a telescope with clockwork can take a photograph of a comet.

Well, it was supposed that comets moved in