4H POPULAR LECTURES AND ADDRESSES. 



Navigation, under whose charge this light is, 

 that the long-short-long-short would be thoroughly 

 free from liability to be mistaken for the occult- 

 ing light (short-short) off Garvel point, three miles 

 from it, and would, in the circumstances, give it 

 a more telling characteristic quality than a single 

 eclipse in the period, or than any group of three 

 eclipses. 



It will be seen, from the preceding Table of 

 occulting lights that, with the exceptions of Holy- 

 wood Bank, Craigmore, Garvel Point, Chapman, and 

 Cardross, the distinction in each case is only a single 

 eclipse in the period, and that, except in nine of 

 them, the period is one minute or upwards, but in 

 all, except five, the duration of the eclipse is less 

 than half a minute. In all the more recent eclipsing 

 lights the period is half a minute or less, and the 

 duration of the eclipse is at most five seconds. The 

 tendency, undoubtedly, is to quicken the action still 

 further, following the example of the old Point 

 Lynus Light, with its eight seconds of visibility 

 and two seconds of eclipse. 



The necessity for a very short period is not so 



