MODIFICATIONS OF THE QUANTITATIVE SYSTEM OF 
CLASSIFICATION OF IGNEOUS ROCKS 
WHITMAN CROSS, J. P. IDDINGS, L. V. PIRSSON, H. S. WASHINGTON 
During the nine years that have elapsed since the publication 
of the Quantitative System of Classification of Igneous Rocks it has 
been used with increasing frequency by petrographers in all parts 
of the world. Naturally, it has been chiefly employed in conjunc- 
tion with the qualitative system as a means of more exact defini- 
tion, and as an aid in the correlation and comparison of rocks from 
different regions. Besides the commoner rocks that belong to the 
systematic divisions for which magmatic names were originally 
suggested, numerous varieties have been described that belong to 
divisions not named by the authors of the system, and some that 
were not known to exist at the time of its publication. For these 
divisions magmatic names have been suggested by petrographers 
from time to time, and the following have come to our attention 
since the first appearance of the system in 1902: 
I. 2.2.3. Cardiffose (F. D. Adams and A. E. Barlow, 1910). 
I. 3.1.4. Taurose (H. S. Washington, 1904). 
Tesia3 Piedmontase; I. 5.3.4. Piedmontose (T. L. Watson and 
S. Taber, 1912). 
I. 5.3.2. Mazarunose (H. S. Washington, 1903). 
I. 5.5.4-5. Caledonose (Lacroix, 1911). 
I. 6.2.3. Procenose (H. S. Washington, 1906). 
I. 6.2.5. Raglanose (F. D. Adams and A. E. Barlow, 1908). 
I. 7.1.2. Craigmontose (F. D. Adams and A. E. Barlow, 1908). 
I. 7.1.3. Appianose (H. S. Washington, 1906). 
I. 8.2. Monmouthase; I. 8.2.4. Monmouthose (Adams and Barlow, 
1908). 
Lot 7-5: -Indare; Teqqe 7-5. © Unalase; “iy jip.e, 5) tase ralosem (Eas 
Washington, 1903). 
It]. 1.5.3. Dungannonase; I.]]. ;.5.3.4. Dungannonose (Adams and 
Barlow, 1908). 
Iq]. 1.5.4. Borsowase; I.[]. ;.5.4.3. Borsowose (H. S. Washington, 
1903). 
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