8 THE ART OF PROJECTING, 



CHAPTER II. 



ARTIFICIAL LIGHTS. 



While it is true that sun-light is much brighter than 

 artificial light, and is therefore very desirable as the illu- 

 minating agent in projections, it is also true that sun- 

 light is not always to be depended upon, and it will fre- 

 quently disappoint one, by reason of clouds, which will 

 entirely prevent using the porte lumiere and the ex- 

 periment will need to be postponed until the sky is 

 again clear. In some circumstances such delay would 

 be no serious matter, and one could very well wait ; at 

 other times the delay would be very inconvenient and 

 work some harm in our educational institutions \ hence 

 recourse is had to artificial light and lanterns. As 

 nearly every kind of projection is possible in this way, 

 and some persons will be provided with such instru- 

 ments, and still others who would like to know what 

 can be done with lanterns, some space will be given to 

 descriptions of some of their more common forms and 

 their applications. 



THE ELECTRIC LIGHT. 



Chief among the artificial lights used in projecting 

 is the electric light, which is produced when a powerful 

 current of electricity is made to pass between two 

 carbon points which are separated a short distance from 

 each other. It is necessary to have a current of elec- 



