﻿Air fyc.for Pure Notes of (liferent Pitch. 2">7 



Mv results for air may 1x3 summed up as follows : — 



1. Tho velocity of sound in narrow glass tubes is smaller 

 than in tho open air ; it increases with the diameter of the 

 tube and the pitch of the note. 



2. Tho loss which the velocity of sound suffers in narrow 

 glass tubes is inversely proportional to the diameter and the 

 square root of the vibration-frequency. In other words, the 

 formula 



7 



a—v= y= 



is correct if a, the true velocity, =330*582 metre*, nndy, the 

 constant for friction and conduction of heat, =0'007 ( J8 ( J. 



3. The ratio of the specific heats for air is 1'3D47 *. 



§ 4. Carbonic Acid. 



The alteration of the apparatus necessary for the application 

 of this method to gases depends upon the density of the gas. 



For carbonic acid everything remained the same as for air, 

 with the exception of a small change at the side-piece A. 



As the main tube had to remain open, the chief difficulty 

 lay in keeping the gas pure. The air could either, by dif- 

 fusion, penetrate into the tube, or, by the lowering of the 

 water-column, be drawn into it. The difficulty was over- 

 come in the following manner. 



The three arms of a T (fig. 2) were fitted with pieces of 

 gutta-percha tubing, of which the one led to the side tube A, 

 the other to the gas-apparatus, and the third to the ear of the 

 observer. The T-piece was fixed so high and so inclined to 

 one side, that the heavy gas flowed in a natural manner into 

 the main tube. 



The gas was generated in a Kipp's apparatus from oyster- 

 shells and hydrochloric acid, and conducted through a system 

 of wash-bottles and pearl-tubes saturated with a solution of 

 sodium carbonate. The method of filling was as follows : — 

 The swimmer was raised to A and the stopcock H closed. 

 After the gas had flowed a short time through the ear-tubing, 

 it was firmly clamped. The gas could now only escape 

 through the side piece A, and thus the air still remaining in 

 the upper portion of the main tube was rapidly expelled. The 

 open end at was then made air-tight and the stopcock H 

 opened. The energy of the generation of the gas drove the 

 water out of tho tube back into the bottle, but always against 

 a small counter-pressure, as I always took care that the surface 

 * Corrected on page 264. 



