LIGHT-HOUSES. 



117 



TUB MAQIO I.ANTEBN. 



object placed near the focus of the light, and throwing it 

 upon a screen across the room, where many persons can 

 see it together. 



The first purpose, however, for which the need of a very 

 bright light was felt by mankind was to increase the range 

 of illumination spread over the sea from the lanterns in 

 light-houses. Light-houses on sea-coasts have been in use 

 from very ancient times. It is true that, before the inven- 

 tion of the mariner's compass, ships were very seldom taken 

 intentionally far out of sight of land. But they were at any 

 time liable to be driven off the coast by sudden storms, or 

 to have shores that were near hidden from view by mists, 

 or fogs, or driving rain ; and sometimes their voyage would 

 be protracted by unfavorable winds, so that night would 

 come on before they had entered their destined port. 



