Dynamical Illustration of the Isothermal Formula. 301 



explosion very rarely takes place, owing to the fact that liquid 

 is carried up to the spark-gap by the rush of gas, and a 

 minute drop almost always adheres to the ends of the wires 

 forming the spark-gap, so that no spark, and consequently 

 no explosion, is produced. 



This difficulty, however, can be easily overcome by con- 

 necting the two halves of the resonator with a battery of 

 three or four cells, so that as soon as a minute drop is formed 

 across the spark-gap it is at once dissipated by the current 

 which passes through it. If the battery connexions are made 

 at nodes, the proper working of the resonator does not seem 

 to be interfered with, so that the battery may remain in 

 permanent connexion with it. 



Of course the same battery may be used both for getting 

 rid of the drop and for generating the explosive mixture of 

 gases, the circuit which is completed by the drop in the 

 spark-gap being a shunt on the circuit through the electro- 

 lyte. When it is desired to work with a very small spark- 

 gap, we have found it very convenient to include a rough 

 galvanometer in the former circuit, as a small spark-gap can 

 then be very easily made by screwing up H, stopping directly 

 a deflexion is obtained, and then screwing H back very 

 slightly so as just to break the circuit. 



In our first experiments we used dilute sulphuric acid as 

 the electrolyte instead of hydrochloric acid ; but we found 

 that when the spark was very small, it failed to explode the 

 mixture of oxygen and hydrogen produced. When, however, 

 hydrochloric acid is used, so far as we have observed, every 

 spark, even the smallest we have been able to obtain, pro- 

 duces an explosion, provided of course that the tube is 

 properly filled with gas. 



In conclusion, it might be well to add that the tube which 

 we have found to work very satisfactorily is 16 centim. long 

 and 8 millim. in diameter (inside), the spark-gap being about 

 5 centim. from the top. 



XXXI. Dynamical Illustration of the Isothermal Formula. 

 By Ladislas Natanson, Phys.D., Lecturer on Natural 

 Philosophy, University of Cracow*. 



IN the Kinetic Theory of Matter it is our object (as will, I 

 think, be generally admitted) to imagine a dynamical 

 model of some definite state of matter and to investigate the 

 properties of the mechanism conceived. 



* Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 33. No. 202. March 1892. Y 



