816 Transactions of tue American Institute. 



Pkopagation of Sound in Tubes. 



M. Iviindt has made a series of elaborate experiments to determine 

 the velocity of sound in tubes. He finds that the velocity dimin- 

 ishes with the diameter of the tube, but this diminution only becomes 

 sensible when the diameter is equal to one-fourth of the length of the 

 air-waves producing a given sound. Starting with this diameter, he 

 finds the velocity of sound diminishes with the increase of pitch, or, 

 in other words, the velocity increases as the length of the air-waves 

 increase. In tubes of small diameter he discovered that fine powder 

 distributed over the interior, checked the progress of sound in direct 

 proportion to the quantity and lightness pf the powder ; yet a rough- 

 ness in iho, tube itself does not retard sound. The amplitude of the 

 air-wave or the intensity of sound was found to produce no influence 

 on the rate of propagation. In this connection we may allude to the 

 experiments recently made by M. Regnault of the French Institute. 

 He used the new sewers in the city of Paris for the purpose of deter- 

 mining the force of the air waves producing sound. By firing a pis- 

 tol in tubes and sewers of various diameters, he found that the sound 

 was carried, in a passage 4.2 inches in diameter, through a distance of 

 1,282 yards ; in a passage 11.8 inches in diameter, 4,191 yards ; in a 

 passage forty-three inches in diameter, 10,494. The manner of con- 

 structing the tube, and the material of which it is composed, exercises 

 a great influence on the rapidity with which sound is transmitted. 



LiQUIFTIKG LaUGHINCJ GaS. 



The uniform efficiency and safety of laughing gas as an anesthetic 

 has prompted The British Medioal Journal to suggest that a bottle 

 be made strong enough to hold the gas in a liquid form, and of such 

 weight and dimensions that it may be easilj^ carried by the surgeon 

 in his daily rounds. At present it is used by dentists from large bags, 

 into wiiich it is placed as soon as made. Laughing gas is composed, 

 according to the new notation, of two atoms of nitrogen and one of 

 oxygen. These two elements are the principal constituents of com- 

 mon air. Laughing gas, or nitrous oxyd can be liquified under a 

 pressure of T50 pounds per square inch, when at the temperature of 

 forty -five degrees Fahrenheit. The most convenient and safe recep- 

 tacle for the'liquid would be a brass or copper tube, not more than a* 

 foot in length, and of such thickness as to resist a pressure of at least 

 1,500 pounds, or several small tubes of the ordinarj- thickness might 

 be united side by side and made entirely safe. 



