476 SPECIAL METHODS OF DISCOVERY. 



the heavens. The discovery of the satellites of Jupiter 

 was almost immediately the reward of his activity ; and 

 these were announced in the " Nuncius Sidereus," pub- 

 lished at Venice in 1610. The title of this work will 

 best convey an idea of the claim it made to public notice. 

 "The Sidereal Messenger, announcing great and very 

 wonderful spectacles, and offering them to the considera- 

 tion of everyone, but especially of philosophers and astro- 

 nomers ; which have been observed by Galileo Galilei, &c., 

 by the assistance of a perspective glass lately invented by 

 him ; namely, in the face of the moon, in innumerable 

 stars in the Milky Way, in nebulous stars, but especially 

 in four planets which revolve round Jupiter at different 

 intervals and periods with a wonderful celerity ; which, 

 hitherto not known to anyone, the author has recently 

 been the first to detect, and has decreed to call the 

 Medicean stars" ' ' These events are a remarkable in- 

 stance of the way in which a discovery in art may influ- 

 ence the progress of science.' ! By means of the telescope 

 which he had erected in the gardens of the Quirinal at 

 Rome, Gfalileo, in the year 1611, observed dark spots on 

 the surface of the sun, and found that they changed their 

 forms and dimensions, and sometimes merged into each 

 other ; other astronomers also observed the spots about 

 the same period. The invention of the telescope also led 

 to improvements in the grinding of lenses, and to the 

 study and discovery of various phenomena and laws of light. 

 6 William Herschel, a man of great energy and inge- 

 nuity, who had made material improvements in reflecting 

 telescopes, observing at Bath on March 13, 1781, dis- 

 covered in the constellation Gemini, a star larger and less 

 luminous than the fixed stars. On the application of a 



1 Whewell, History of tJie Inductive Sciences, vol. i. 3rd edit. pp. 300-303. 



