9'PEAKING TRUMPETS, 



287 



pet and the fpeaking trumpet not being a fufficient reafon for 

 retaining it, it is probable that it would have been laid afide, 

 in the fame manner as the contour of the trumpet was aban- 

 doned, when the form and dimenlions moft fuitable to this in- 

 ftrument were fought for by experimental trials. There would 

 alfo have been another inducement to difpenfe with it, becaufe 

 HatTe had already omitted it in the fpeaking trumpet which 

 he indicated as preferable to thofe of Morland and Caflegrain. 

 I afcertained by experiment that two fpeaking trumpets of the Which is con- 

 fame length and the fame diameter produced different efFeds ^"jJ^J° ««?«"- 

 when they were terminated by an enlarged aperture or not, 

 and that in general this enlargement confiderably increafed the 

 intenfity of the found. The beating of my watch which I 

 heard at 4"*. 2, the mean diftance of feven experiments (a) 

 by placing it at the mouth of a fpeaking trumpet of 0". € long 

 and 0™. 38, mean diameter of the tube, was not heard beyond 

 2"^. 25, mean diftance of feven experiments (a) when I placed 

 it in a tube of the fame length and the fame diameter. Thus 

 the caufe which occafions this aperture to ftrengthen the fooner 

 is different from the reflection of the fonorous rays. 



Since the refled^ion of found does not in any manner concen- This Is further 

 Irate the fonorous rays in a cylindrical tube, it muft follow, as Fo^ed by the 

 Lambert has concluded in his Theory of Refledion, that fpeak- augmented in 

 ing trumpets with cylindrical tubes fliould notfenfibly augment ^P^^^"g trum- 

 the found. To prove whether experiment agreed with this drical tubes ^ as' 

 theory, I immediately conflrudted a fpeaking trumpet, with a ftrongly as in 

 cylindrical tube of 0«. 26, the length of the cylinder, 0'". 25, ^^.^^^fj^! ''''"'' 

 the length of the enlarged part, 0". 035, the diameter of the , 



cylinder, and 0*". 190, the greateft diameter of the enlarged 

 part, and, by comparing the intenfity of the found which it 

 produced, with that of a conical fpeaking trumpet of the fame 

 height, and of a fimilar mean diameter, J afcertained that tiie 

 jftrength of the found was fenfibly the fame. In both, the beat- 

 ing of my watch, which I did not hear in the open air beyond 

 1". 08, fnean diftance of five experiments (h) was heard at 

 3". 94, mean diftance of five experiments (b) when I placed 

 it at the mouth of either fpeaking trumpet. Since the cylin- 

 drical fpeaking trumpet ftrengthens the found in the fame man- 

 ner as that which is conical, and iince, on the contrary, the 

 theory of reflection fhows that it ftiould not be ftrengthened, 

 it follows that the augmentation of found in thefe inilrumen.t* 

 .»rifes from a caufe different from reflection. 



One 



