THE ATMOSPHERE AND FOG-SIGNALING. 701 



out the low boom of the cannon continued audible after all the other 

 sounds had ceased. 



But it was only during the early part of the day that this prefer- 

 ence for the longer waves was manifested. At 3 p. m. the case was 

 completely altered, for then the high-pitched siren was heard when all 

 the other sounds were inaudible. On many other days we had illus- 

 trations of the varying comparative power of the siren and the gun. 

 On the 9th of October, sometimes the one, sometimes the other was 

 predominant. On the morning of the 13th the siren was clearly heard 

 on Shakespeare's Cliff, while two guns, with their puffs perfectly vis- 

 ible, were unheard. On October 16th, two miles from the signal-sta- 

 tion, the gun at eleven o'clock was inferior to the siren, but both were 

 heard. At 12.30, the distance being 6 miles, the gun was quite 

 unheard, while the siren continued faintly audible. Later on in the 

 day the experiment was twice repeated. The puff of the gun was in 

 each case seen, but nothing was heard ; in the last experiment, when 

 the gun was quenched, the siren sent forth a sound so strong as to 

 maintain itself through the paddle-noises. The day was clearly hos- 

 tile to the passage of the longer sonorous waves. 



October 17th began with a preference for the shorter waves. At 

 11.30 a. m. the mastery of the siren over the gun was pronounced ; at 

 12.30 the gun slightly surpassed the siren; at 1, 2, and 2.30 p. m. the 

 gun also asserted its mastery. This preference for the longer waves 

 was continued on October 18th. On October 20th the day began in 

 favor of the gun, then both became equal, and finally the siren gained 

 the mastery ; but the day had become stormy, and a storm is always 

 unfavorable to the momentary gun-sound. The same remark applies 

 to the expei'iinents of October 21st. At 11 a. m., distance 6^ miles, 

 when the siren made itself heard through the noises of wind, sea, and 

 paddles, the gun was fired ; but, though listened for with all attention, 

 no sound was heard. Half an hour later the result was the same. 

 On October 24th five observers saw the flash of the gun at a distance 

 of 5 miles, but heard nothing ; all of them at this distance heard the 

 siren distinctly ; a second experiment on the same day yielded the 

 same result. On the 27th also the siren was triumphant ; and on 

 three several occasions on the 29th its mastery over the gun was very 

 pronounced. 



Such experiments yield new conceptions as to the scattering of 

 sound in the atmosphere. No sound here employed is a simple sound ; 

 in every case the fundamental note is accompanied by others, and the 

 action of the atmosphere on these different groups of waves has its 

 optical analogue in that scattering of the waves of the luminiferous 

 ether which produces the various shades and colors of the sky. 



Concluding Remarks. A few additional remarks and suggestions 

 will fitly wind up this paper. It has been proved that in some states 



