MODERN SCIENCE. 253 



indicating the presence of hydrogen and nitrogen among 

 them a character showing these nebulae to be gaseous 

 bodies in an evolutionary stage towards the constitution of 

 suns, thereby strengthening the nebular hypothesis of Laplace. 

 He also discovered that comets yield a spectrum consisting 

 of a few (three or four) luminous bands much wider apart 

 than those in the nebulae : they too exhibit the character 

 of gaseous bodies. He discovered in the light of Jupiter, 

 Saturn, and Mars, several lines like those exhibited by our 

 own atmosphere, thus proving that these planets are sur- 

 rounded by an atmosphere like the earth, though certainly 

 of a different degree of density. Some stars which he 

 studied he found to be wrapped by a metallic atmosphere 

 like our sun : Aldebaran contains antimony, bismuth, 

 mercury, and tellurium, which are not found in the sun, 

 and hydrogen, iron, calcium, magnesium, and sodium which 

 are present in the sun. In Pegasi and Batelgeux (a- 

 Orionis), he found no hydrogen, although he found that 

 gas in all the other stars which he has studied by the side 

 of many other substances, some of which have not yet 

 been found upon the earth. Dr. Huggins, among other 

 phenomena as regards the motion of stars, found that 

 SlRlUS was moving away from us at the rate of 25 miles 

 per second. That in our ignorance of the actual distance 

 from us of Sirius and of a multitude of very remote stars, 

 for we indeed know the distance of very few the nearest 

 yet we should be able to determine the velocity of their 

 motions is another wonder due to the magical spectroscope, 

 for the instrument reveals the motion of distant bodies, 

 " by the alteration which it causes in the apparent rapidity 

 of vibration, and consequently in the refrangibility of rays 

 of light of definite colour/' For it must be remembered 

 that (i) the undulations of the luminiferous ether cause the 

 points of the retina to vibrate and produce the sensation 

 of light ; (2) that any given colour depends upon the rapidity 

 of light waves impinging upon the eye; (3) that the eye 

 will receive in a second less undulations from a body 

 receding from it, and more undulations from a body 

 moving towards it, just as an anchored boat will be struck 



