340 THE WORLD MACHINE 



earth, like the sun, they are flying, flying, flying. Is there any 

 way that we can compute their speeds ? 



In front of the window near where I write, lies the Golden 

 Gate of the Pacific, famed in the legends of the newer Argonauts. 

 Across it, as I write, a ship sails slowly. Its distance, the width 

 of the Gate, are known. It is needful only to time its passage 

 to know how fast the ship is sailing. It is the same with the 

 stars whose distance we know. 



Bessel had chosen the star numbered 61 Cygni, for measure 

 of its parallax, because of its relative rapid motion across the 

 line of sight. When he had computed its distance it was not 

 difficult to reckon its speed. It came out at nearly forty miles 

 per second. As cosmic motions go, it was not great. Some of 

 the planets, some of the comets, move as swiftly. But consider 

 that this star is not a planet, not a tenuous comet. It is a sun ; 

 it is doubtless carrying in its train a company of satellites like 

 unto our own system. 



It taxes the imagination to conceive even the rate of motion 

 of our own earth. One can count five, at the utmost ten in 

 a second. In each of these counts our earth has flashed on 

 several miles along its pathway around the sun. The star in 

 the Swan that we number 61 is moving twice as fast. You may 

 multiply the speed of the earth by ten ; and there are stars 

 moving more swiftly still, one of them the greatest star of the 

 northern firmament. 



The first of these terrific speeds to be discovered was the 

 celebrated " run- away " star known as 1830 Groombridge that 

 is, a star otherwise so insignificant that it has merely a number 

 in the Groombridge catalogue. It is apparently moving at 

 somewhere near two hundred miles per second, perhaps more. 

 The vast sun of Arcturus is moving more swiftly still. Some 

 recent estimates set its speed at between four and five hundred 

 kilometres, possibly three hundred miles or more per second. 

 So far as we know, there is nothing like it in the universe. Of 

 the stars whose speeds may be reckoned there is nothing ap- 

 proaching it save in the instance named. Most of those that 

 are known move at comparatively moderate speeds like our own 

 sun. But our knowledge of the stellar universe as yet is slight. 

 For aught we know, there may be others whose rate of trans- 

 lation is vastly beyond that of Arcturus itself. 



Three hundred miles per second ! Let us try a minute to 



