2i8 THE NATURAL HISTORY [LETT. 



were as audibly and intelligibly returned as the first ; and there 

 is no doubt, could trial have been made, but that at midnight, 

 when the air is very elastic, and a dead stillness prevails, one or 

 two syllables more might have been obtained ; 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 off. Buildings, or naked rocks, 

 re-echo much more articulately than hanging wood 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 source of this echo, as we found by various experi- 

 ments, is the stone-built, tiled hop-kiln in Gally-lane, which 

 measures in front 40 feet, and from the ground to the eaves 12 

 feet. The true centrum phonicum, or just distance, is one par- 

 ticular spot in the Kings'-field, in the path to Xore-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 120 feet for the return of each syllable distinctly : 

 hence this echo, which gives ten distinct syllables, ought to 

 measure 400 yards, or 120 feet to each syllable; whereas our 



1 "A monster griin, tremendous, vast and high." 



(DKYDEN'S Virg, JEn. iii. 658.) 



