242 
NATURAL HISTORY 
midniglit, when the air is very elastic, and a dead stillness 
prevails, one or two syllables more might have been ob- 
tained; but the distance rendered so late an experiment 
very inconvenient. 
Quick dactyls we observed succeeded best ; for when we 
came to try its powers in slow, heavy, embarrassed spondees 
of the same number of syllables, 
"Monstrum horrendum, informe, ingens 
we could perceive a return but of four or five. 
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 oflP. Build- 
ings 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 ex- 
periments, 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 dis- 
tance ; 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 exact- 
ness, and found the distance to fall very short of Dr. Plot's 
rule for distinct articulation ; for the Doctor, in his " History 
of Oxfordshire,^' allows 120 feet for the return of each syl- 
lable distinctly; hence this echo, which gives ten distinct 
syllables, ought to measure 400 yards, or 120 feet to each 
syllable ; whereas our distance is only 258 yards, or near 
seventy-five feet to each syllable. Thus our measure falls 
short of the Doctor's, as five to eight ; but then it must be 
acknowledged that this candid philosopher was convinced 
