400 POPULAR LECTURES AND ADDRESSES. 



then first placed on the Royal Sovereign shoal ; 

 the Group Flashing Light of Mr. Hopkinson, in 

 which, instead of just one flash in the period, there 

 are, in the case of the Royal Sovereign Light, three 

 flashes in the period, or, as may be in other cases, 

 two flashes, or four flashes, the interval between 

 the successive flashes of the group being much 

 shorter than the interval from group to group in 

 the whole period. In two cases in the English 

 Channel, the North Sand Head and the Casquets, 

 the new triple flashing light was introduced to 

 replace, by a group of three flashes in rapid 

 succession, three separate lights which had been the 

 characteristic arrangement previously ; three fixed 

 lights in the case of the North Sand Head, and 

 three simple flashing lights in the case of the 

 Casquets. 



Mr. Preece has imprudently pointed out that Mr. 

 Hopkinson's triple flashing light is the letter S of 

 the Morse-Colomb flashing alphabet. Sailors, we 

 may hope, are happily ignorant of this truth, 

 otherwise the proverbial captain of the collier 

 would be calling out to his chief officer " Bill, was 



