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Swansea Harbour Trust.


-------Local Chartering.





Micros Photography and Armour…

Diamonds and X-RRYA-

The Mystery of the Echo


The Mystery of the Echo fhe sconce of acoustics is, as yet, in its hfanoy, ind men nave much to learn before they <. .n solve the mystery of tfee echo or predict her fleeting moods, writes Miss G-ertrude Bacor in ^o»d Word* tolatea in general terms the explanation of erhcw simple and easy to understand. SounC, as we know, is conveyed +,0 us by vibrations of the aiif, which spread around from the source of sound Katactly as waves of —iter spread in ever widening fftngs when a pebble Is thrown into a still lake. Very frequently it happens that these wavea of IOWld, in their outward course, strike against some Surface of such a nature that they are, by it, ieflected bac\ again without being broken and Scattered. Aud when it occurs that these wave* <M returned at iuch an angle as to strike the ear of a listener, we have what we call an echo. Often More than one reflection goes to th* making up ot an echo, the sound-waves being thrown from ov* •orfaee to another in their passage to the ear-jusf M a billiard ball will rebound from cushion V oashion on its way round the table. This, roughil do the cai-,se of the phenomenon. But so endles* Me the variations of circumstances ind inTiron- WMnt, and the effects they produce so far-reaching and hard to foresee, that we are continuaUy being taken unawares. Sometimes ¡-.he echo returns at fwickly that it cannot be distinguished front th* Mnglnal sound; and yet its undetected pret- aoce is enough to affect seriously the penetration Off a coice in a church or theatre Sometimes enc found will produce several echoes in different directions, which return and return again at different time intervals, to the great distraction ot fee hearers- Again the surface of the reflecting Object has a great deal to do with the nature M the echo returned. Certain substances seem to bave a tendency to absorb the sound-waves, aai Others to eflect them more readily. Another curious property of sound-waves, exemplified in many wall- V»owia buildiBgs, is the tendency » the waves te run found a apse or galle*<% aouch as » iravo of the sea, striking aslant on a shallow bay, Will mn round the shflft. This is th# explaaatta* ■ many familiar ac-onMtic curio*iti<-s. not*My M SifSMMs Whiaj^ring ttoUocy «( St. It+ml'