COMPLICATION OF HEAT PROBLEM OF THE EARTH. 593 



mechanical action, produced by chemical action, transferred to within the 

 zone of fracture by volcanism, and derived from the interior by conduction, 

 so far as it escapes is largely transferred by means of water. If this con- 

 clusion be true the question immediately arises as to the effect upon the 

 temperature gradient. 



Barus states that, because of the chemical action of water in the pores 

 of rocks, heat is liberated; and that we may consider the zone of circula- 

 tion as a furnace. From this he concludes that the temperature gradient 

 observed is probably not high enough, on the average, or the "observed 

 rate of increase of temperature with depth is too large."" The reasoning 

 applied to heat developed by chemical reactions would apply to that pro- 

 duced by mechanical action in the zone of fracture and to that introduced 

 by volcanism. But in Barus's statement the fact that the water is in circu- 

 lation is altogether neglected. This makes the case much more complicated 

 than Barus supposed. The water is in circulation, and, as already shown, 

 is constantly abstracting heat from the earth. Therefore it appears that, 

 aside from volcanism, from the zone of fracture heat is being transferred to 

 the surface in two ways — by conduction and by the convectional circula- 

 tion of water. I suspect that the heat convectionally transferred by 

 circulating waters is as great as or greater than that lost by conduction. 

 The amount thus transferred by convection may more than compensate for 

 that developed within the zone of fracture by mechanical and chemical 

 action and by volcanism. 



The above suggestions are offered to show that the problem of the 

 heat gradient is much more intricate than has been supposed, and that the 

 heat problem of the earth can not be treated as a simple one in which con- 

 duction is the only factor to be handled. The problem is so complicated 

 by chemical action, by mechanical action, by igneous intrusions and 

 extrusions, and by the water circulation in the zone of observation, that 

 any conclusion as to the loss of heat of the earth and the depth to which 

 cooling extends which ignores these disturbing factors is of very little value, 

 to say the least. 



a Barus, Carl, The compressibility of liquids: Bull. U. S. Geol. Survey iS T o. 92, 1S92, pp. S3-8-t. 

 HON XLVII — 04 38 



