3UI THEORY or EAR TRUMPETS. 



tales of wood, with which I made an unsuccessful experiment 

 on the ears of a lady who labours under a considerable degree 

 of nervous deafness. An attempt was also made to convey 

 weak sounds by the same instrument to the auditory organs 

 through the medium of the teeth, when the ears were stopped ; 

 but att these trials failed, unless the sonorous body happened 

 to touch some part of the apparatus. 



This succession of disappointments convinced me, that 

 solid conductors can be of no advantage to the partially deaf. 

 ^Probable use of Instances of great insensibility may occur indeed, in which 

 •^lid cofaduc-^e may arrive at the seat of hearing by their assistance, 

 through the channel of the mouth, after every trial to ap- 

 proach it by the natural ducts and passages have proved 

 'fruitless. In this manner, perhaps, some persons apparently 

 in a state of absolute deafness, might acquire some idea of 

 the musical scale by attaching one end of a stick to a harpsi- 

 chord, and holding the other in the mouth. At the same 

 time, lam apprehensive your correspondent A. B. will be un- 

 fortunately disappointed in his expectations of relief from 

 conductors, which are to be held in the teeth in the manner 

 of a tobacco pipe. 

 Anexperiment The next experiment relates more directly to ear trumpets, 

 trumpet. ^"^ discovers the mode in which they operate on the auditory 



organs. I took a hollow copper cone, the mouth of which 

 ^ was finches in diameter, and having closed one of ray ears 

 with wet paper; I introduced the small end of the tube into 

 the other, taking care to cover that side of my face with a 

 ^ 'folded handkerchief, with a view to intercept as much as 



possible such vagrant pulses as were not received by the 



* trumpet. Upon directing the wide end of my clumsy instru- 

 tnent towards a' watch on'a' table, I found that it rriagnified 

 the strokes of the balance beyond my expectation. But this 



* was the case only while the tube remained open, for the 

 watch ceased to be audible after a plug of wet paper had 

 been forced into the narrow part of the tube, at the distance 



Trumpets con- ^f ^ ^^ 3 inches frorri the smaller extremity. This experi- 

 Hense sonori- nflent poihts out the officfe of an ear trumpet in ii satisfactory 

 ferous pulses. , , • i i .111 



manner. Its business is to condense the pulscsvvhich happen 



' tO" fall into its cavity, and thereby to discharge them \yith 

 ' ' ■ ■ ' greater 



