116 



ILLINOIS STATE ACADEMY OF SCIENCE 



the inner tube. The data taken for tube No. 1 are given 

 in Table II. 



1L 



c 



D 



V 



L — 



Fig. 1 



The variation of the pitch with the length of tube No. 

 1 is shown graphically by Curve 1, Fig. 2. 



Other tubes were constructed in which the diameters 

 of the inner and outer tubes, and the lengths of the inner 



