140 Mr. Willis on the Presstire of a Stream of Air, Sfc. 



from the center, they must necessarily increase their distance from 

 each other, and hence the air in the annulus becomes suddenly 

 rarefied, by which means its progressive velocity and the pressure 

 on the preceding and succeeding portions is variously modified. 

 Some of these modifications I have attempted to develope ex- 

 perimentally, and have ventured to submit these results to the 

 Society in the hope that they may be found useful hereafter in 

 confirming any theoretical views of the subject which may appear, 

 and in the mean time may serve to throw some light on a phe- 

 nomenon which is doubtless possessed of very great interest. 



R. WILLIS. 



C/vius College, 

 April 21, 182S. 



