56 TRANSACTIONS. I9OI-2 



fore lie favours less intense and longer flashes, but the general 

 practice today is to greatly reduce the length of flashes and 

 the dark intervals between -them ; and some of our old- 

 fashioned revolving lights, having a period of two or three 

 minxites, are hopelessly out of date. 



F g Signals. The increase in speed of ships, to which I have 

 alluded, and in ihe quantity of shipping, as well a-^ the haste 

 insisted upon in these days of close competition, have made it 

 imperative that ships should push on through fair weather and 

 foul, through clear weather and thick, and all our prominent 

 turning points are piled np with the wrecks of the vessels 

 that have cnt the corners too closely. In the endeavour to 

 protect vessels under these conditions fog alarms have become 

 more and more necessary, and more and more relied upon as 

 aids to navigation, and are now found upon most salient head- 

 lands. These may be classified under four heads, viz : — 

 (i) Explosive signals. 



(2) Sounds produced by reed instruments. 



(3) Whistles, and 



(4) Sirens. 



The one advantage of explosive signals is the facility 

 with which they can be established. The necessary electri- 

 cal connections can be made in a few minutes, and their in- 

 stallation costs practically nothing, especially since gun cotton, 

 exploded in the open air at the end of a mast, has taken the 

 place of gunpowder fired from cannons. 



A disadvantage of an explosive signal is that the noise is 

 so short in duration that it may be drowned in a local noise, 

 lost in the noise of the waves, or of a storm, or even in the 

 roaro: the gale in the rigging ; moreover, it is difficult to fire 

 with safety so frequently as modern requirements demand ; if 

 fired frequently explosive signals become much more expen- 

 sive than more powerful and prolonged noises produced at 

 frequent intervals by machinery. Canada is therefore aiming 

 to replace explosive signals by steam or compressed air fog 

 sirens. 



