IGNEOUS PPIENOMEXA AXD CAUSES. 271 



tion that the basic lavas are hotter than the acid,* though Button talks 

 of their superfusion, and though there are numerous indirect indications 

 that this is the case. Therefore I would suggest direct measurements of 

 the temperature of acid lavas as a fruitful field for inquir}^ While we 

 often hear of white-hot basic lavas, I have never heard of white-hot acid 

 lavas. They are more viscid,t although this may be due to the different 

 chemical character. Then again I do not know, nor have I found records 

 of rhyolites baking adjacent rocks, as basalts sometimes do. Acid rocks 

 also are said to have less effect on enclosed fragments than basic ones 

 have.j; Then again the fluid enclosures, et cetera, in granite point to no 

 very high temperature. I think that this cannot so truly be said of the 

 certainly primary enclosures in basic eruptives. It is, of course, to be 

 remembered that it is very unsafe to argue from the temperature at which 

 lava is emitted as to its initial heat. Finally, the less oxidation of the 

 iron in the basic and plutonic rocks, as evinced in the prevalence of 

 magnetite over hematite, of green colors over red, and of h^'persthene 

 and olivine over biotite, et cetera,§ and directl}^ in the analyses collected 

 by Iddings,|| is a very strong argument for the relation suggested. In 

 other words, we 'know-that rocks grow heavier and hotter toward the 

 center of the earth, and in rocks furnished by volcanoes we find increas- 

 ing weight associated with signs of increasing heat and with increasing 

 amount and decreasing oxidation of iron. Continue this process and we 

 must come to a core in which unoxidized iron is a prominent factor. 



Chemical Complexity of igneous Rock Series. — Suppose now that this 

 theory of igneous phenomena be accepted, what further deductions can 

 we draw from it, and how far can they be verified? In the first place, 

 we see that the material fed into the volcanic funnel will be at first from 

 more than one level. Thus the series from acid to basic rocks will not 

 be a simple one,^ since a magma of a given silica percentage may be 

 produced either by a mixtui'c from a wide range of depth or by matter 

 from more nearly one deptli ; yet one can see that there would be cer- 

 tain limits to the variation thus produced. Moreover, the cracks might 

 cross, within the region of feeding, the lines of old intrusions or erup- 

 tions, and thus other variations be produced. This mixture of rocks 

 from difterent levels might result in heating due to chemical reactions 

 and would certainly tend to produce a corrosive effect. That the intra- 



*Geilvie : Op. cit., p. 222. 



t (^eikie : Op. cit., p. 247. 



tLarrroix: Neues Jahrbuoli, vol. i, 1892, p. GT. 



gde Lapparent : Comples Rendus, February 18, 1889, p. 369. 



II U. S. Geol. Survey, Annual Report, 1801, pp. 629-649; see also Ransonie : Bull. Department of 

 Geo!. University of California, vol. i, 1893, p. lOfi. 



^Rosenbusch: T. M. P. M., vol. xi, 1890, p. 144. See also Neues Jahrbnoh vol. i, 1891, p. 61, and 

 vol. 2, 1891, p. 56. 



