274 A. C. LANE GEOLOGIC ACTIVITY OF THE EARTLl's GASES. 



on the rocks of southern Norway contains a mass of facts bearing in tKis 

 direction, and his pneumatolytic theory is directly in line with our argu- 

 ment. The relation of pegmatites and micropegmatite is close, and I 

 believe both to be formed from water-charged magmas. 



I have a specimen in which a quartz-felspar vein is backed by and 

 gradually passes into a beautifully developed graphic granite. The 

 micropegmatite or granophyric texture has in many cases been shown 

 to be secondary, by Bayley, Williams, Irving, and Romberg, and is con- 

 sidered to be always so by Wadswarth. We must either give it up as a 

 primary texture entirely or class it in the last pneumatolytic stage. 



Formation of Veins. — I do not care to dwell on the subject of veins, but 

 would merely call attention to the fact that in the recognition of the im- 

 portance of these exuding gases the theory of filling by ascent would 

 have a powerful support. It has been remarked that we have an almost 

 continuous series from volcanoes to hot springs. Why should we not 

 have an almost continuous series of rocks ? So, too, certain kinds of 

 ores are genetically connected with certain rocks, as tin with granites, 

 and nickel and mercury (cinnabar) with serpentines, which is readily 

 accounted for by supposing the veins to be charged with the condensed 

 gases from them. 



Magmatic Zones. 



Relation of Depth and increasing Pressure and Temperature. — We have 

 generally talked of gas, but it is obvious that the actual temperature and 

 pressure may at times make them liquid. It must be remembered, how- 

 ever, that above a certain temperature no amount of pressure will liquefy 

 a gas, although the gas may occupy no more space than the fluid. Thus 

 temperature is on the whole the most important factor, pressure but 

 serving somewhat to neutralize it. When we come to chemical reactions, 

 however, the effect of pressure may be more considerable ; but this is not 

 yet determined. With the rapid strides that theoretical chemistry is 

 making, in the hands of Barus and others, we may soon hope to know. 

 Then from studies of blast-furnace reactions we may advance our knowl- 

 edge of the earth's interior, for it is obvious, according to the theory 

 here outlined, that the likeness of volcanic action to that of a blast fur- 

 nace is striking. In both we have iron at the bottom, above a reducing 

 and basic zone and yet above an oxidized zone. Similarly the temper- 

 ature decreases going upward, and similar gases are absorbed or in chem- 

 ical activity. 



I have therefore prepared Table II, showing the increasing pressure 

 and increasing temperature, relative to the depth from the earth's sur- 

 face. By the side of the pressure column I have placed the crushing 



