CHAP, iv. I THE TELESCOPE. 249 



CHAPTEE IV. 



THE TELESCOPE. 



THE microscope enables us to penetrate into the mysteries of the 

 infinitely small ; it places the most minute objects within range of 

 human sight, and exhibits in a distinct manner the thousand details 

 with which the unaided eye is powerless to deal. 



That which the microscope does for objects within our reach, but 

 too small to be visible, the telescope realises with a similar power for 

 objects which are rendered indistinct by distance, whatever their real 

 dimensions may be. It fathoms the depths of space, and presents to 

 the view, stars, the existence of which, without its help, would 

 scarcely ever have been guessed ; while with regard to those which 

 can be seen with the naked eye, it reveals to science the details of 

 their structure, and thus multiplies for our curiosity the objects 

 which nature offers to observation, and by the aid of which human 

 intelligence interprets her laws. 



The word telescope is taken from the Greek, as in the case 

 of the microscope ; both have a common root, a/coi-eco (scoped), I 

 look, piKpos (micros}, small, and T/;Xe (tele], afar. Etymology 

 therefore applies the word telescope to all instruments which magnify 

 objects and bring them nearer to the eye. Thus we have refracting 

 telescopes, that is, instruments formed of certain combinations of 

 glasses or lenses ; and reflecting telescopes, that is, instruments with 

 a mirror or reflector. 



I. PiEFKAoriNG TELESCOPES. 



With regard to the date at which telescopes were invented, and 

 the name of the inventor of this wonderful instrument for celestial 

 and terrestrial investigation, there is some .uncertainty, as in the case 



