12 THE MICROSCOPE AND ITS LESSONS. 



eye has been telegraphed to the brain by the optic nerve, 

 the black pigment has absorbed the remainder of the 

 image, and that marvellous window of the soul is ready 

 for more work. 



Amongst the countless host of the heavens there is a 

 constellation known to astronomers under the sign of 

 " Cygnus," the Swan. Fifty years ago, Sir John Herschel 

 wrote that one of the stars in this constellation was 

 among the most interesting he had seen. Its motion 

 is so extraordinary that Arago supposed its velocity 

 to exceed that of Mercury the most rapid body of our 

 solar system sixty thousand times. ~ The distance of 

 this swanlike group of stars known as Cygnus is 

 stated to be 657,700 times the radius of our earth's orbit, 

 or nearly 6272 billions of miles. 



Supposing one of these distant worlds to be in a state of 

 conflagration, we should know nothing of it until a ray of 

 light reached our eye which had started on its journey, 

 travelling at the express rate of 192,000 miles every 

 second ten years before we beheld it. To make this 

 more intelligible, a cannon-ball, rushing through space 

 at the average rate of five hundred miles an hour, 

 would require 14 millions of years to reach that star. So 

 insignificantly minute is the reflection of this atom, that 

 the delicate thread of a spider's web placed before the 

 eye of a spectator, supposing there to be one at this star, 

 would conceal from his view the whole orbit of the earth, 

 the diameter only of which is nearly 200 millions of miles, 

 the circumference nearly 600 millions ; but what is our 

 earth to the solar system? the whole of which might 

 be hidden from the eye of the supposed spectator by a 

 single hair ! 



But what has this to do with the assembly at Paris ? 

 Much every way. Formerly this stellar witness to the 



