470 



SCIENTIFIC RECREATIONS. 



Fig. 497. Radii Vectores. 



Fig. 496. Ellipse. 



came into use. The actual discoverer of this now almost perfected instru- 

 ment is uncertain. Borelli, who 

 wrote in the seventeenth century, 

 ascribes the discovery to Zacha- 

 riah Jansen and Hans Lipper- 

 sheim, spectacle makers of Mid- 

 dleburg. Baptista Porta, also a 

 spectacle maker, has had the 



credit of discovering the magnifying power of the 

 lens, and, so far, the originator of the telescope. 

 But whoever invented it, the telescope did not penetrate into southern 

 Europe till 1608-9. Galileo then made inquiries concerning the new instru- 

 ment, and Kepler made some propositions for their construction. But 

 Harriot had used the instrument so far back as 1 6 1 1 or 1612, and had 

 observed spots upon the sun's disc. Galileo, in 1610, had also made obser- 

 vations with the telescope, and discovered the satellites of Jupiter. He 

 thereby confirmed the Copernican theory;* and when Newton promulgated 

 his immortal discovery of gravitation, after Picard's researches, the relations 

 of the sun and planets became more evident. His researches were published 

 in the Piincipia> and then one-half the scientific world began to question the 

 principle of gravitation, which was supported by Newton and his adherents. 

 Subsequently the researches of Lagrange and Laplace, Adams and Leverrier, 

 Sir J. Herschel, etc., brought astronomy into prominence more and more ; 

 and the innumerable stars have been indicated as new planets have been 

 discovered. The spectroscope, which gives us the analyses of the sun and 

 other heavenly bodies, has, in the able hands of living astronomers, revealed 

 to us elements existing in the vapours and .composition of the sun, etc. 

 Stars are now known to be suns, some bearing a great resemblance to our 

 sun, others differing materially. The 

 nebulae have been analysed, and found to 

 be stars, or gas, burning in space hy- 

 drogen and nitrogen being the chief con- 

 stituents of this glowing matter. Instru- 

 ments for astronomical observation have 

 now been brought to a pitch of perfec- 

 tion scarcely ever dreamed of, and month 

 by month discoveries are made and re- 

 corded, while calculations as to certain 

 combinations can be made with almost 

 miraculous accuracy. The transit of 

 Venus, the approaches of comets, eclip- 

 ses, and the movements of stars, are Fig. 49 8.-Ecii P tic and Equator. 



*He was obliged to recant before the Inquisition, and to repudiate his researches. He 

 was released on the condition of observing silence upon the theory he had supported, but 

 again obliged to recant. 



