KEFKACTION OF SOUND BY THE ATMOSPHEEE. 
319 
approaching the Well light-ship, which is six miles from the Roaring Middle Buoy. 
There was now a very light breeze again, so we set up our sail to get steering-way on, 
and fell down with the tide. We presently heard a rocket go up and explode, hut we 
could make no impression with our signals : we found on returning that they had com- 
pletely lost sight of us ; nor was this surprising considering that we were in a small 
boat and the sun was directly behind us. A breeze sprang up, so we returned to the 
yacht, where on comparing notes we found that we had heard every call as well as 
report. During the interval in which we had no answers, Major Hake, who had been 
answering my calls, having completely lost sight of us, had gone below to get some lunch ; 
in the mean time the men on deck had heard our calls, but not having instructions had 
not answered them. 
To sum up the results of our excursion : — We had called and been answered up to 
three miles and a half, and our calls as well as the reports of the rockets had been heard 
to more than five miles. 
Incidentally I noticed that we could occasionally hear the reports of guns from the 
shore, which was more than eight miles distant ; and once while listening for an answer to 
one of my calls, I distinctly heard a dog bark, which must have been on shore, as there 
was no boat between us and it except the yacht. All the time we could distinctly hear 
the paddles of a steamer, which at the time we were at the Roaring Middle was in the 
Wisbeach Channel, or nine miles from us and fifteen from the yacht, on which her 
paddles were also distinctly heard. 
It appears to me that the distances at which sounds of such comparative low intensity 
were heard over the water this day is beyond any thing definitely on record. One hears 
casually, however, of remarkable instances : once in this district I heard of a clergyman 
who from the Hunstanton side of the Wash heard a man hammering a boat on the 
Wisbeach side. When one thinks, however, of the extreme difficulty of identifying a 
sound with its source at three or four miles distance, it is no matter of surprise that 
such phenomena should for the most part escape notice. On this day, had we not been 
purposely on the look out, I do not think any thing we heard would have attracted our 
attention. I have often heard the rifles of volunteers over tolerably flat country seven 
miles ; and, as I have previously stated, the guns of the naval review at Portsmouth were 
heard by many persons, including myself, in Suffolk, over a distance of 170 miles * 
With regard to the cause of the exceptional distances over which we heard the sounds 
on the 19th of August, 187 4 ; as was only natural, my attention was all the while directed 
to this. For the sake of my experiments, what I had been in hope of was a state of the 
atmosphere which would cause great upward refraction of the sound, and I was natu- 
rally on the qui-vive for any indications of such a state. All the morning I had been 
watching the distant objects to see whether they were lifted or depressed by the refrac- 
tion of light. They loomed to a remarkable degree, which showed that the upward 
* They -were also heard by Sir "William Thomson, who was on hoard his yacht about 10 or 15 miles to the 
west of Portland, and therefore 180 miles from Doyer. 
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