88 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



stances, including hydrogen and carbon monoxide, stream from all 

 azimuths in the magma chamber to the lower end of the conduit. The 



pipe has always a very much 

 smaller cross-section than the feed- 

 ing chamber, implying some con- 

 centration of the volatile matter. 

 (Figures 7 and 8.) At conduit 

 temperatures this ever-varying 

 mixture of gases must, according 

 to practically infinite probability, 

 be in unstable chemical equililib- 

 rium ; under the conditions new 

 equilibria are attained with the 

 evolution of heat. 



The relative proportions of each 

 gas must, in general, be different 

 from that in the primary magma 

 before it was injected. Concentra- 

 tion of the gases means, according 

 S U B 3 T R AT U M ^^ ^^® ^^^^ ^^ mass-action, the de- 



Figures. Ideal cross-section through velopment of new compounds. As 

 middle cone shown in Figure 7, to same *^^® pressure is less m the conduit 

 scale. than in the underlying chamber, 



the viscosity of the magma is less, 

 the gas bubbles are larger, and the speed of possible reactions is thereby 

 increased. 



Of course, the actual amount of heat evolved during the chemical 

 rearrangements in the conduit cannot be estimated, but a glance at the 

 following tables (showing some examples) must assure one that the 

 heat product from the complex system may be of a high order. 36 



Heats of Formation. 



^* The values for the heats of formation and reaction are taken from the 

 works of Thomsen, Muir and Wilson, Xernst, and others. In some cases 

 more recent experiments give slightly different values. 



