VOL. XIV.] PHILOSOPHICAL TRANSACTIONS. Q 



be likewise made for the proportionable decrease of the sound according to its 

 distance. 2. As a convex speculum reflects the object less, but somewhat 

 brighter or clearer: so a convex obstacle repels the sound smaller, but some- 

 what quicker, than otherwise it would be. 3. As a concave speculum reflects 

 the object larger, but more obscure and inverted: so a concave obstacle echoes 

 back the sound louder, slower, and also inverted ; but never according to the 

 order of words. 4. As a speculum takes in and reflects more of its object, 

 when placed at a great distance from it than when nearer ; because it reflects 

 according to the apparent magnitude of the body at such a distance, which is 

 less : so also the echoing body, being removed farther off", reflects more of the 

 sound than when nearer. And this is the reason, why some echoes repeat but 

 one syllable, some one word, and some many. 5. As speculums may be so placed, 

 that reflecting one upon or into the other, either directly or obliquely, one 

 object shall appear many ; as in Sir Samuel Moreland's glass-room : after the 

 same manner echoing bodies may be so contrived and placed, as that reflecting 

 the sound from one to the other, either directly and mutually, or obliquely and 

 by succession, out of one sound shall many echoes be produced; Moreover a 

 multiple echo may be made, by so placing the echoing bodies, at unequal dis- 

 tances, that they reflect all one way, and not one on the other; by which means 

 a manifold successive sound will be heard; one clap of the hands like many, one 

 ha like a laughter, one single word like many of the same tone and accent, and 

 so one viol like many of the same kind imitating each other. P^urther, as spe- 

 culums may be so ordered, that by reflection they shall make one single thing 

 appear many different tilings; as one single man to seem many men, differing 

 as to shape and complexion, or a company of men, wh-ch I think Sir Samuel 

 Moreland's contrivance does not: so may echoing bocVies also be ordered, that 

 from any one sound given, they shall produce many echoes, different both as to 

 their tone and intention. By this means a musical room may be so contrived, 

 that not only one instrument, played on in it, shall seem many of the same sort 

 and size; but even a concert of different ones; only by placing certain echoing 

 bodies so as that any note played shall be returned by them in 3"^, 5'% and 8"", 

 which is possible to be done otherwise than was mentioned before in refracted 

 audition. 



Forfarther improving this noblescience, the followingproblemsareproposed: — 



1 . The first is, to make the least sound, by the help of instruments, as loud 

 as the greatest; a whisper to become as loud as the shot of a cannon. By the 

 help of this problem, the most minute sounds in nature may be clearly and 

 distinctly heard. 



2. The second is, to propagate any the least sound to the greatest distance. 

 VOL. in. C 



