CLASSIFICATION OF IGNEOUS INTRUSIVE BODIES 507 



The other principles of classification — viz., b), c), d), and e) — are 

 applied in the classification now to be presented in a manner suffi- 

 ciently obvious to need no discussion. Principle e) is less funda- 

 mental than the others, excepting d,) and is recognized as appearing 

 only occasionally in the scheme : the major diameters of true lacco- 

 liths tend to horizontality; a principal axis of a bysmalith, neck, 

 stock, boss, or batholith is characteristically vertical. 



It is obvious that transitional forms are to be expected among 

 the related types of the classification. These forms have not been 

 mentioned in the table, which would thus have become overburdened. 

 Magmatic differentiation within the chambers of dikes, sills, stocks, 

 etc., has often produced varietal types of these bodies, but the pro- 

 cess has occurred too irregularly to permit of its furnishing a con- 

 venient criterion for the general classification. 



PROPOSED CLASSIFICATION OF IGNEOUS INTRUSIVE BODIES 



A. Masses due to injection of exotic material. 

 I. Injection along planes of stratification in invaded formation. 



1. Intrusive sheets. 

 a) Sills. 



(1) Simple. 



(2) Multiple. 



(3) Composite. 



b) Interformational sheets. 



2. Laccoliths. 



(1) Simple. 

 Symmetric. 

 Asymmetric. 



(2) Compound. 



(3) Multiple. 



(4) Composite. 



(5) Interformational. 



II. Injection across planes of stratification in invaded formation. 



1. Dikes. 



(1) Simple. 

 Dike-networks. 



(2) Multiple. 



(3) Composite. 



2. Eruptive veins. 

 Contemporaneous veins. 



3. Apophyses or tongues. 



