8 PHILOSOPHICAL TRANSACTIONS. [aNNO l683-4. 



that they shall receive in sounds made at a very great distance also; but with so 

 much advantage, that the ear shall be able to hear them, which otherwise would 

 have been inaudible. Again, as microscopes or magnifying glasses, help the 

 eye to see near objects, that by reason of their smallness were invisible before : 

 so microphones or micracoustics, that is, magnifying ear instruments, may be 

 contrived so that they shall render the most minute sound in nature distinctly 

 audible, by magnifying it to an inconceivable loudness; by the help of which we 

 may hear the different cries and tones, as well as by microscopes see the divers 

 shapes and figures of the smallest animals. Also, as by polyscopes or multiply- 

 ing glasses, one thing is represented to the eye as many, whether in the same 

 or different shapes ; so by a polyphone or polyacoustic, well ordered, one sound 

 may be heard as many, either of the same or a different note. Insomuch that 

 who uses this instrument will at the sound of a single viol seem to hear a whole 

 concert, and all true harmony. By which means this instrument has much the 

 advantage of the polyscope. 



Reflected vision has been improved by the invention of looking-glasses and 

 polished metals, whether plane, concave, or convex. Thus also reflected audi- 

 tion, made by echoes, may be improved, by contriving several sorts of artificial 

 echoes. For in general, any sound falling directly or obliquely on any dense 

 body, of a smooth surface, is beat back again and reflected, echoes more or 

 less. But if the sound be propagated parallel to the surface of the dense body, 

 there will be no reflection of sound, no echo. Or if the surface of the opposing 

 body be uneven, the air by reverberation will be put out of its regular motion, 

 and the sound be thereby broken and extinguished : so that though in this case 

 also the air be reflected, yet sound is not reflected, nor is there any echo. And 

 if it does echo more or less, to show, that when all things are as is before de- 

 scribed, there is still an echoing, though it be not always heard, either because 

 the direct sound is too weak to be beaten quite back again to him that made it; 

 or that it does return home to him, but so weak that without the help of a good 

 otacoustic it cannot be discerned ; or that he stands in a wrong place to receive 

 the reflected sound, which passes over his head, under his feet, or to one side 

 of him ; which therefore may be heard by a man standing in that place, where 

 the reflected sound will come, provided no interposed body does intercept it; 

 but not by him that first made it. 



I shall further make out the comparison between reflected vision and audition 

 by these following propositions. 



1. As a plane speculum reflects the object in its due dimensions and colours ; 

 allowing for their difference of appearance according to their distance : so a 

 plane obstacle reflects the sound back in its due tone and loudness ; if allowance 



