450 Intelligence and Miscellaneous Articled 



The stoppage of the vibrations by the mass of- exterior air, the 

 form, still unknown, of the gaseous vein, the too feeble elasticity, 

 of the fluid, may contribute together or separately to the prevention 

 of any acoustic impression. 



In order to strengthen the sounds originally produced at the 

 orifice from which the flow takes place, for the purpose of submit- 

 ting to a further investigation the laws of the vibrations of columns 

 of air, a cylindrical pipe of wood was fixed np(ra,the metallic plate, 

 so that its axis passed through the centre rf; the acoustic -aperture.- : 



When air was forced through by the bellbwjs a sound waspro- 

 duced, and the vibrations were communicated tolthe pipe, whjeh gave 

 out a series of harmonics comparable in point of , purity -and- inten- 

 sity with the finest sounds of the organ. 



The results of these experiments upon the motion- of air in tubes 

 may be expressed as follows :-y 



1 . Air in flowing from an orifice acquires a yilpratpry condition 

 capable of producing sound in gaseous columns. 



2. The acoustic phenomena are not altered by placing the orifice 

 on the upper or under part of the pipe through which the air flows*, 

 or by forcing or drawing the air through it. 



3. The sounds which any one pipe is capable of giving depend 

 only on the pressure of the air and not on the diameter of the ori- 

 fices. The number of vibrations appear to be, for a constant aerial 

 pressure, proportional to the thickness of the plates. 



4. The different harmonics of a pipe vibrated by air issuing 

 through a circular orifice may be thus classified : — > , 



a.. Several sounds deeper .than the fundamental sound of the 



Pipe- .. 'W 



b. Sounds of the open pipe, agreeing with theory. 



c. Sounds of the closed r pipe, agreeing with theory. 



d. Indeterminate sounds. 



e. Harmonic sounds of the theoretic wave. 



5. The space comprised between two ventral segments or two 

 nodes of vibration is always conformable to theory, with the excep- 

 tion of a. portion of the pipe near the plate, 



Terminated by two ventral segments, or by one ventral segment 

 and one node, this portion is generally much smaller than an actual 

 wave. 



6. The acoustic wave, situated at the extremity of the pipe, which 

 is the seat x>f the initial vibratory motion, and the real or theoretic 

 wave at a distance from this, always vibrate in unison, and their 

 lengths bear a simple and harmonic ratio to each other. 



7 . For the same orifice in the same pipe a sound may be produced 

 by very different pressures, but they still preserve an harmonic pro- 

 portion to each other. 



8. For any one sound the pressure varies within certain limits, 

 without the tone of the pipe manifesting the slightest alteration ; it 

 is only the intensity of the sounds which increases or decreases with 

 the pressure. 



9. One pipe may give several sounds simultaneously. 



10. To a given mouth-piece, a pipe possessing the property of 



