Signalling and Safety at Sea. 9 



with quite sufficient accuracy for safe navigation in fog, 

 from distances far beyond the range of aerial log signals if 

 the vessel is equipped with receivers. If the light-vessels 

 round the coast were fitted with submarine bells it would be 

 possible for ships fitted with receiving apparatus to navigate 

 in fog with almost as great certainty as in clear weather." 

 In spite of this report t!ie multiplication of submarine bell 

 stations was slow in England. The first was installed off the 

 Mersey in December, 1906. The Irish Lights Commissioners 

 placed a submarine bell on the Kish Bank Lightship in 1909. 

 The submarine bell is in some cases operated electrically ; 

 more especially for use off the coast on the floor of the sea. 

 A power station on the coast supplies the requisite current. 

 The bell is suspended from the apex of a steel tripod about 

 25 feet high and weighing 3 tons, a cable being taken 

 ashore. The depth varies down to 25 fathoms. ISuch a bell 

 is located off the Stack Lighthouse, Holyhead. The fre- 

 quency of the bell-stroke is controlled by rotary time 

 switches. In the United States this system came into use as 

 early as 1901. 



Finally the submarine bell-buoy claims our attention. 

 This is a simple and effective signalling machine and one which 

 may be maintained at small annual cost. The buoy carries 

 the bell and its simple mechanical mechanism housed beneath 

 it in a boiler-plate receptacle which is open below, the bell 

 alone partly protruding. Thus the mooring chain cannot 

 foul the bell or its operating mechanism. The motive power 

 is entirely derived from the wave energy of the >ea. The 

 mechanism is such that the energy imparted by the rising 

 and falling of the buoy to a hinged vane immeised beneath 

 is accumulative. A spring is compressed by the movement 

 of the buoy, whether this be up or down. Each oscillation 

 thus compresses the spring a little more till when a certain 

 compression is produced the spring is released and in the 

 act of release causes the hammer to strike the bell. The 

 uniform intensity of the blows is thus secured. The fre- 

 quency of the strokes depends on the state of the sea, but, 

 as already mentioned, is never less than three or four strokes 

 per minute. To secure the mechanism against the rusting 

 effects of sea-water the chamber holding it is filled with oil ; 

 any leakage of which is made good from a small tank above. 

 The recognition of sound by those on the vessel presents 

 a problem of equal importance with that which we have been 

 considering. It is requisite not only to receive the ?ound, 

 but to receive it in such a manner as to enable the sailor to 

 determine the direction from whence it proceeds. 



