I9OI-2 TRANSACTIONS. 57 



The earlier trumpets and horns, operated by steam or air, 

 were reed instruments, but these have been found less power- 

 ful than whistles and sirens, and are being rapidly replaced by 

 the latter, although good horns have given surprising results. 

 On one occasion I heard the horn on the Western Islands, in 

 Georgian Bay, distinctly at Cape Croker, 26 miles distant, 

 across a wind. 



It is questionable if any sound can be produced superior 

 to the clear blast of a good steam whistle, and many of our 

 best fog alarms are large whistles. The sound can be varied 

 by changing the intervals between the blasts and by the use 

 of various modifications of whistle bells. Chime whistles are 

 used, as well as whistles containing a piston, which changes 

 the length of the bell and consequently varies the note. 

 These variable whistles are known as "Modoc" or "Wild Cat" 

 whistles. You will ail remember the distinctive, if disagree- 

 able, sound of the whistle that was on Eddy's factory, pre- 

 vious to the fire of 1900. 



In the siren the sound is produced by forcing steam or 

 air through small holes opened and closed very rapidly by 

 the revolution on a perforated metal disk of another similarly 

 perforated disk. By varying the number of openings or the 

 speed of the revolution, the pitch or tone of the siren is 

 changed. At Belle Isle I installed a 6-inch siren in 1899, 

 giving alternately a high and a low note. 



The air compressors here are driven by a jet wheel, with 

 water led from lakes on the hills of the island, and the com- 

 pressed air is piped for 4000 feet to the horns. This alarm is 

 of the largest and most powerful type ever installed at any 

 station, aad is the only example of a fog alarm run by water 

 power. 



One disadvantage of all fog signals except steam whistles 

 is that the trumpets throw the sound out in one direction, so 

 that it- is louder in the axis of the trumpet than in other 

 directions. There seems, however, to be no way of over- 



