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All echoes have some one place to which they are returned 

 stronger and more distinct than to any other; and that is 

 always the place that lies at right angles with the object of 

 repercussion, and is not too near, nor too far off. Buildings, 

 or naked rocks, re-echo much more articulately than hanging 

 woods or vales ; because, in the latter, the voice is, as it were, 

 entangled, and embarrassed in the covert, and weakened in 

 the rebound. 



The true object of this echo, as we found by various experi- 

 ments, is the stone-built, tiled hop-kiln in Gaily Lane, which 

 measures in front forty feet, and from the ground to the eaves, 

 twelve feet. The true centrum phonicum, or just distance, is 

 one particular spot in the King's Field, in the path to Nore- 

 hill, on the very brink of the steep balk above the hollow 

 cart-way. In this case, there is no choice of distance ; but 

 the path, by mere contingency, happens to be the lucky, the 

 identical spot, because the ground rises or falls so immediately, 

 if the speaker either retires or advances, that his mouth would 

 at once be above or below the object. 



We measured this polysyllabical echo with great exactness, 

 and found the distance to fall very short of Dr Plot's rule for 

 distinct articulation ; for the Doctor, in his History of Oxford- 

 shire, allows one hundred and twenty feet for the return of 

 each syllable distinctly ; hence this echo, which gives ten dis- 

 tinct syllables, ought to measure four hundred yards, or one 

 hundred and twenty feet to each syllable ; whereas our distance 

 is only two hundred and fifty-eight yards, or near seventy-five 

 feet to each syllable.* Thus our measure fells short of the 

 Doctors as five to eight ; but then it must be acknowledged, 

 that this candid philosopher was convinced afterwards, that 

 some latitude must be admitted of in the distance of echoes, 

 according to time and place. 



When experiments of this sort are making, it should always 

 be remembered, that weather and the time of day have a vast 



There is an account in the Memoirs of the French A cademy of a similar 

 echo near Rouen. The building which returns it is a semicircular court- 

 yard ; yet everyone of the same form does not produce a similar effect ED. 



A knowledge of the progression of sound is not an article of mere 

 steril curiosity, but in several instances useful ; for by this means we are 



abled to determine the distance of ships, or other moving bodies. 

 Suppose, for example, that a vessel fires a gun, the sound of which is 

 heard five seconds after the flash is seen, as sound moves one thousand one 

 hundred and forty-two English feet in a second, this number, multiplied 

 by nve, gives the distance of five thousand seven hundred and ten feet 



icsame principle is applicable in storms of lightning and thunder. ED. 



