1874.] On the Adiabatics and Isothermals of Water. 451 



that the mixture surrounding it was explosive, shots were fired from a 

 gun at a distance of 30 yards. The barrel of the gun which was used is 

 U of an inch in diameter, and it is rifled for a length of 3 ft. with 

 seven grooves ; the breech which received the charge is smooth-bored, 

 and 4J inches long. Each measure of gunpowder weighed 3 - 822 grammes 

 ( = 59 grains), and the charges fired ranged between 1 and 9 measures ; 

 paper tamping was rammed down tightly, and the charge was fired by a cap. 



The gun was tied to a prop in the middle of the mine, with its barrel 

 at an angle of about 35 upwards, pointing towards the apparatus ; the 

 muzzle was 18 inches from the floor. At the part where the experiments 

 were made, the sizes of the mine are : width at top, 4 ft. ; width at 

 bottom, 6 ft. ; height, 5 ft. 6 in. 



The sound-wave from a shot of two measures extinguished the flame 

 of the Davy lamp when it was placed on the outside of the apparatus ; 

 but when it was placed in the inside of c?, the flame could not be extin- 

 guished nor passed through the meshes, even when the quantity of gun- 

 powder was raised to nine measures. However, after the lamp had been 

 allowed to burn in the isolated space for a few minutes (the supply of 

 fresh air not being very good), its flame could be extinguished by tfie 

 sound-wave from a shot of four measures. The whole quantity of fire- 

 damp was so small that there was no opportunity for enlarging or varying 

 the apparatus. 



These experiments, and one which I made formerly in the sewer with 

 the b tube of the apparatus, fig. 2, Plate VI., show that a very slight 

 obstacle will interfere with the action of the sound-wave. They were 

 concluded in March 1874. 



I would add, in concluding, that the liberal grant of money which I 

 received from the Government-Grant Committee of this Society has been 

 of great value in enabling me to carry out these experiments. 



I have also been much indebted for assistance to each of the following 

 gentlemen: Mr. Robert H. Scott, E.R.S.; Professor A. C. Eamsay, 

 F.R.S. ; Professor W. W. Smyth, F.R.S. ; Professor Marreco, of the 

 College of Physical Science, Newcastle-on-Tyne ; Mr. John Galloway, of 

 Barleith and Dollars Collieries; Mr. J. B. Simpson, of Newcastle-on- 

 Tyne ; Mr. Charles Shute, of Hebburn Colliery ; and to Mr. William 

 Kirkwood, of the Inkerman Mines, near Glasgow. 







XX. " On the Adiabatics and Isothermals of Water." By.A. W. 

 RUCKER, M.A., Fellow of Brasenose College, Oxford. Com- 

 municated by R. B. CLIFTON, M.A., F.R.S. ,, Professor of 

 Experimental Philosophy in the University of Oxford. 

 Received June 4, 1874. 



M. Verdet, in his work on Thermodynamics (' CEuvres/ vol. vii. p. 184), 

 enunciates the proposition " Deux courbes de nulle transmission ne pen- 



