592 A TREATISE ON METAMORPHISM. 



United States, are many spring's the temperatures of which vary from 

 30° to 100° C. For instance, in the Yellowstone Park are a great 

 number of hot springs and geysers, the temperatures of which approximate 

 100° C. That a vast amount of heat is brought to the surface by the 

 underground circulation of this district can not be doubted. The number 

 of springs in the Cordilleran region which are known as hot is very small 

 as compared with those which are simply warm. The warm springs, 

 according to Gilbert," may be considered as those having a temperature 

 between 18.3° and 37.7° C. (65° and 100° F.) or practically blood heat 

 According to Gilbert, 6 the water of all the foregoing spring's exceeds the 

 mean annual temperature of the air by 8.3° C (15° F.). 



Although we have no data by which to verify the statement, I have 

 no doubt whatever that the number of springs the temperature of which is 

 slightly but measurably above the mean annual temperature exceeds many 

 times the total number of all spring's the temperatures of which are so notably 

 above the normal temperature of the region as to be called warm or hot. 

 Finally, it is highly probable that the amount of water which escapes 

 through notable springs is small as compared with that which reaches the 

 drainage of the valleys through small openings and seepage. The move- 

 ment of this water is relatively slow, and it may be presumed that it is at 

 but a slightly higher temperature at the point of issue than the average 

 temperature of the rocks of the surface. But it is to be remembered that 

 a slightly higher temperature of issuing water over that of the entering 

 water through the vast number of springs of very moderate temperature, 

 and through seepage, is probably of far greater quantitative importance 

 than the marked increase of temperature in the comparatively few warm 

 and hot springs. This illustrates the old principle that widespread small 

 forces and agents may be of more importance, sometimes incomparably 

 more, than the more conspicuous but more circumscribed forces and agents. 



In other regions of recent orogenic movements and volcanism essen- 

 tially the same facts prevail as in the Cordilleran region of America; and 

 therefore observation, so far as it has gone, confirms the g'eneral reasoning 

 given on pag'es 590-591, that water issues from the belt of cementation at 

 a higher temperature than it enters it. 



Aside from the matter of metamorphism, this conclusion has a bearing 

 upon the refrigeration of the earth. The heat of the earth produced by 



a Gilbert, cit, p. 148 b Gilbert, cit., p. 149. 



