1827.] Transference of Heat by change of Capacity. 



ultimately there remained nothing in several of the receivers 

 but a brown substance, heavy, adhesive like honey or treacle, 

 and in certain cases even almost solid. From the circumstances 

 of the experiments, no hesitation could arise in concluding that 

 a spontaneous chemical change had taken place ; and it does 

 not seem at all unlikely that a similar change, or one to a 

 much greater extent, may have occurred suddenly during the 

 rapid alteration in the mechanical condition of the gas in Mr. 

 Gordon's experiment ; the most condensable of the substances 

 in the mixture of elastic matters which constitute oil-gas, being 

 perhaps those which are most altered, and in that case Mr. 

 Gordon's account of the phenomena would be correct. 



Transference of Heat by change of Capacity in Gas*. 



MANY of the copper vessels in which gas is compressed at the 

 Portable-Gas Works are cylinders from two to three feet in 

 length, terminated by hemispherical ends. These are attached 

 at one end to the system of pipes by which the gas is thrown 

 in, and being so fixed, the communication is opened ; it fre- 

 quently happens, that gas previously at the pressure of thirty 

 atmospheres in the pipes and attached recipients, is suddenly 

 allowed to enter these long gas-vessels, at which time a curious 

 effect is observed. That end of the cylinder at which the gas 

 enters becomes very much cooled, whilst, on the contrary, 

 the other end acquires a considerable rise of temperature. 

 This effect is produced by change of capacity in the gas ; for, 

 as it enters the vessel from the parts in which it was previously 

 confined, at a pressure of thirty atmospheres it suddenly ex- 

 pands, has its capacity for heat increased, falls in temperature, 

 and consequently cools that part of the vessel with which it 

 first comes in contact ; but the part which has thus taken heat 

 from the vessel being thrust forward to the further extremity 

 of the cylinder by the successive portions which enter is there 

 compressed by them, has its capacity diminished, and now 

 gives out that heat, or a part of it, which it had the moment 

 before absorbed ; this it communicates to the metal of that 

 part of the gas-vessel in which it is so compressed, and raises 



* Quarterly Journal of Science, xxiii. 474. 



