418 POPULAR LECTURES AND ADDRESSES. 



My proposal for giving character to fixed lights 

 is at present definitely limited to the ten varieties 

 shown in the following table the short eclipse 

 being one second, the long three seconds, in every 

 case, except the one-short and the long-short-long- 

 short. In these the short eclipse is a half-second ; 

 and the long eclipse is three half-seconds. 



It is to be remarked that the times stated in the third and fourth 

 columns need not be known or noted to let the light be recognised. 

 The description in the second column, "short-short," for instance 



1 This characteristic is very easily read, and may be used with 

 advantage in cases in which there is no practical difficulty in obtain- 

 ing speeds corresponding to the times half-second and three half- 

 seconds for the short and long eclipses. 



