3o8 



PRINCIPLES OF STRATIGRAPHY 



shire. (Lapworth and Watts-20: 5^2.) A remarkable modifica- 

 tion of such intrusions through later folding is described by Balt- 

 zer (i) from the Aarmassive, in the Alps. In the Aletschhorn 

 (4,198 meters high) he finds that the schists which form the summit 

 of the mountain rest discordantly upon the surface of the granite, 



Fig. si. Diagrams illustrating intrusive masses. A. Laccolith (Mt. Holmes, 

 Henry Mts., Utah). B. Compound laccolith (El Late Mountains, 

 Colorado). C. Laccolith with subsidiary sheets (Judith Alts. 

 tjpe, Montana). D. Laccolith with broken cover (Ragged Top 

 Mt, Black Hills, S. Dakota). E. Interformational laccolith 

 (Deadwood Gulch, Black Hills). F. Compound laccolith — cedar- 

 tree type (La Plata Mts., Colorado). G. Abruptly protuberant 

 laccolith (Mt. Hillers, Henry Mts.). H. Asymmetric laccolith 

 (Mt. Marcellina, West Elk Mts., Colorado). K. Intrusion in 

 Little Rocky Mts. (Montana). L. Intrusion in volcanic vents 

 (Island Skye). M. Bysmalith (Mt. Holmes). N. Plutonic plug 

 (Ideal). (After Harker.) 



