THE SCIENTIFIC PERIOD 13 



4. Theory of (filling by) ascension, or filling from below, the latter 

 subdivided into : 



a. By infiltration, or solutions from mineral (thermal) waters. 

 6. By sublimation, or by ascending steam. 



c. By sublimation, or in gaseous condition. 



d. By injection or in igneous fluid state. 



He was thus apparently the first to apply the now time-honored terms 

 "ascension," "descension," and "lateral secretion," though the idea was 

 clearly expressed thirty years before by Cuvier's collaborator, Alexander 

 Brogniart, when, in an attempt to reconcile the Huttonian and Wer- 

 nerian schools, he showed that no one theory could fit all kinds of veins. 



The theories of contemporaneous formation and of descension had by 

 this time become practically obsolete among the Germans, and had 

 never had much standing among geologists of other nations. German 

 geologists, who have been the most assiduous students of vein phenom- 

 ena in the field, have always been inclined to assume that vein minerals 

 have been deposited by precipitation from aqueous solution, differences 

 of opinion having been mainly as to the provenance of the waters. 

 Doubtless the influence of Werner had much to do with their mental 

 attitude, but it is also to be remarked that this method of formation best 

 fits the ore deposits of their country. 



In England, the home of Plutonism, on the other hand, no very de- 

 cided views on theories of ore deposition were held. John Maccullough 

 in 1821-1823, after a discussion of the Wernerian-Huttonian views, wisely 

 concludes that it is necessary to study nature's processes more closely 

 before a satisfactory theory can be formulated. He enumerates the 

 minerals occurring in ore deposits which may be formed by infiltration 

 or solution and by sublimation, contending that many vein minerals 

 can be produced in either way, and recommends further investigations 

 along that line. 



John Taylor, in his report on mineral veins to the British Association 

 in 1833, makes a similar review and arrives at similarly indefinite con- 

 clusions. 



Later, De la Beche, in his Geology of Cornwall (1839), says : 



"The theories of the day divide themselves into, first, the contemporaneous for- 

 mation of mineral veins with the rocks which enclose them ; second, the filling of 

 fissures formed in rocks by the sublimation of substances driven by heat from be- 

 neath upwards, and, third, the filling of fissures in rocks by chemical deposits 

 from substances in solution in the fissures, such deposits being greatly due to 

 electro-chemical agency." 



The contemporaneous theory, according to him, was still generally 

 held among Cornish miners, but he himself is evidently more inclined 



