TREES AS SHELTER TO GROUND TO THE LEEWARD. 161 
The action of the forest, considered merely as a mechanical 
shelter to grounds lying to the leeward of it, might seem to be 
an influence of too restricted a character to deserve much 
notice; but many facts concur to show that it is a most import- 
ant element in local climate. 
which accompany human industry in countries thickly peopled by man, 
contributes to the same result. We become, by habit, almost insensible to 
the familiar and never-resting voices of civilization in cities and towns; 
but the indistinguishable drone, which sometimes escapes even the ear of 
him who listens for it, deadens and often quite obstructs the transmission 
of sounds which would otherwise be clearly audible. An observer, who 
wishes to appreciate that hum of civic life which he cannot analyze, will 
find an excellent opportunity by placing himself on the hill of Capo di Monte 
at Naples, in the line of prolongation of the street called Spaccanapoli. 
It is probably to the stillness of which I have spoken that we are to 
ascribe the transmission of sound to great distances at sea in calm weather. 
In June, 1853, I and my family were passengers on board a ship-of-war 
bound up the Algean. On the evening of the 27th of that month, as we 
were discussing, at the tea-table, some observations of Humboldt on this 
subject, the captain of the ship told us that he had once heard a single gun 
at sea at the distance of ninety nautical miles, The next morning, though 
a light breeze had sprung up from the north, the sea was of glassy smooth- 
ness when we went on deck. As we came up, an officer told us that he 
had heard a gun at sunrise, and the conversation of the previous evening 
suggested the inquiry whether it could have been fired from the combined 
French and English fleet then lying at Beshika Bay. Upon examination 
of our position we were found to have been, at sunrise, ninety sea miles 
from that point. We continued beating up northwards, and between sun- 
rise and twelve o’clock meridian of the 28th, we had made twelve miles 
northing, reducing our distance from Beshika Bay to seventy-eight sea 
miles. At noon we heard several guns so distinctly that we were able to 
count the number. On the 29th we came up with the fleet, and learned 
from an officer who came on board that a royal salute had been fired at 
noon on the 28th, in honor of the day as the anniversary of the Queen of 
England’s coronation. The report at sunrise was evidently the morning gun, 
those at noon the salute. 
Such cases are rare, because the sea is seldom still, and the xvudrov 
avijpiSpov yéAacue. rarely silent, over so great aspace as ninety or even seyenty- 
eight nautical miles. I apply the epithet silent to yéAacua advisedly. I am 
convinced that Aischylus meant the audible laugh of the waves, which is in- 
deed of countless multiplicity, not the visible smile of the sea, which, belong- 
ing to the great expanse as one impersonation, is single, though, like the 
human smile, ae of the play of many features. 
