THE MAGNETO ELECTRIC MACHINE. 169 



have parallel rays which are thrown forward in 

 a perfectly straight line, as you will see by com- 

 paring the size of the lens with that of the 

 light thrown on the screen. You will now see 

 how far we can affect this beam of light by in- 

 creasing or diminishing the distance of the 

 lamp. We are able by a small adjustment to 

 get a beam of a large or small angle, and observe 

 what power I have now over it ; for if I want to 

 increase the degrees of divergence, I am limited 

 by the power of light in the case of the oil lamp, 

 but with the electric light, I can make it spread 

 over any width of the horizon by this simple 

 adjustment. These then are some of the reasons 

 which make it desirable to employ the electric 

 light. 



By means of a magnet, and of motion, we 

 can get the same kind of electricity as I have 

 here from the battery ; and under the authority 

 of the Trinity House, Professor Holmes has 

 been occupied in introducing the magneto- 

 electric light in the lighthouse at the South 

 Foreland ; for the voltaic battery has been tried 

 under every conceivable circumstance, and I 

 take the liberty of saying it has hitherto proved 

 a decided failure. Here, however, is an in- 



