IMPROVEMENTS IN COAST SIGNALS. 587 



will be observed, on comparing the two codes, that their general efficiency 

 with regard to intensity is nearly equal. With the short and long 

 flashing code a waste of light is obviously incurred with the long flashes, 

 which, for rendering them clearly distinctive from the short flashes, are 

 necessarily three times the length of the latter. "With the white and red 

 flashing code a loss is also incurred in colouring the red flashes, which 

 are required to have the same penetrative power as the white flashes. 

 This loss is found to be 50 per cent, nearly of the initial intensity. It is 

 found that, with the short and long flashing code on a thickly lighted 

 coast, the distinctions are not sufficiently trustworthy ; but, by interposing 

 portions of the white and red code, this difficulty is removed. In the 

 occulting series it will be observed that short and long eclipses are sub- 

 stituted for the short and long flashes of the flashing series, and that the 

 same period of half a minute is proposed. Very fortunately the occulting 

 light is exactly the reverse in appearance of the flashing light. The 

 occulting light is really a fixed light with short eclipses at regular periods, 

 and the flashing light is a flash, or group of flashes, followed by a long 

 eclipse at regular periods. It is, therefore, possible to place occulting 

 lights in close proximity to flashing lights without risk of confusion. 



Of all the various sound signals now in use for the guidance of the 

 mariner during fog, viz., bells, gongs, guns, whistles, trumpets, sirens, 

 and sounds produced by explosions of gun-cotton, the sounds produced 

 by the siren and by explosions of gun-cotton have been found to be the 

 most efficient for first-class fog signals ; therefore these signals have re- 

 cently received the greatest care and attention in their development. 

 The siren doubtless ranks first, chiefly on account of the facility it affords 

 for giving sounds of any desired intensity, pitch, or duration ; while the 

 explosive sound is always of nearly the same pitch, and its duration is so 

 short as to render it liable to be unheard in consequence, rather than from 

 lack, of power. 



The same necessity exists with sound coast signals as with light 

 coast signals for clear and trustworthy distinctive characters ; and it is 

 evident that time as an element of distinctiveness should be avoided, 

 and for the following reasons ; first, the blast, or group of blasts, or ex- 

 plosions, "of a coast fog signal should occupy the same time as the flash 

 or group of flashes of a coast light signal, say 8 to 10 seconds, to enable 

 the mariner on hearing the signal to determine instantly his position by 

 a compass bearing of the sound, which, fortunately, can be accom- 

 plished with sufficient accuracy. 



It is not considered desirable that the periods of a coast fog signal be 

 so short as those of a coast light signal ; indeed, it would appear prefer- 

 able that sound signals be given more as cautionary aids to navigators. 

 First^ in consequence of the uncertainty which necessarily attends the 

 effective range of any sound ; and secondly, the necessity for navi- 

 gators to proceed with the utmost care during fog, to avoid collision 

 with other vessels. Periods of 1, 2, 3, 4, and 5 minutes have been 

 adopted for the siren, and periods of 5, 10, and 15 minutes have 

 been adopted for the explosive signal. The signal of 2 minutes' periods 

 for the siren would appear to fulfil very fairly the required conditions 

 for maximum efficiency. With siren signals sounding one blast of 

 b seconds, or groups of two, three, four, or five blasts of 6 seconds 

 collectively every two minutes, we have 6 seconds of blast to 114 seconds 

 of silence, or as 1 to 19 ; such a signal has, therefore, twenty times 



