ofOXFo %p-S H I %E. ^ 
Geometrical paces, or 120 feet, I guefb'd that tile objefl: could 
not be removed lefs than 400 of the former^ and 2000 of the 
latter. For the better underftanding of which Analyfis^ and for 
the Readers more fecure finding of the true diftance of the 
fpeaker in any other place, it may be convenient that he take no- 
tice, chat all Echo*s have fome one place whither they are return- 
ed ftronger, and more diftindl than any other, and is always the 
place that lies at right angles with the objecl:, and is not too near, 
or too far off: for if a man ftand at oblique angles with it, the 
voice is better returned to fome other perfon at another place^, 
than to the fpeaker ; and fo if he ftand too near, or far oft, al- 
though he do ftand at right angles with it, which is plain by the 
cliagram^Tab, I, Fig. where 
z. the true place of the fpeaker, 
a b. the vocal line fatting at right angles on the ohjeSi. 
cd. places on each hand the trueplace^ and oblique totbeohjeSl, 
e f. places above and below the objeSi^ whence atfo the voice 
comes obliquely to it » 
g h. places whence (Vis true^ the voice goes in right angles td 
the obje5U but g is too far off^ and h too near. 
No w the fpeaker ftanding in a^ and his voice going in the ftraighc 
line a b^ and ftriking upon the objeft fo as to make right angles 
with it, muft needs return to the fpeaker again in the fame line^ 
and no farther, becaufe he is fuppos'd to ftand at the two ex- 
treams of the whole mix'd line of adion : but if he ftand too 
near at ^, then the £ci)o repeats more fyllables, and diftinder at 
g than either at h or a^ bccaufeg is now the extream of the line 
of aftion ; for by how much the nearer the fpeaker is to the ob- 
jeft, by fo much the more forcible he ftrikes it, which caufes the 
rebound to befo much beyond him : and thus if he ftand as much 
too far oft', as at^, then the Echo repeats more fyllables and di- 
ftinder at h, then either at a or g^ becaufe the diftance being too 
great from ^ to Z', and the reflexion weak, the £c/?o muft needs 
terminate fo much the fhorter at ; allthefe being fuppofed to 
take up the whole line of the voices direft and reflex aftion. A- 
gain, if the fpeaker ftand in c obliquely to the objeft, the Echo is 
better heard at d^ than either at ^je or c ; andfo if he ftand zidy 
it is better heard ate then any other place : thus if he ftand at e 
B above 
