176 REPORT OF THE AMERICAN COMMITTEE. 
LL. Do YOU APPROVE THE EUROPEAN MaP CoMMITTEE's 
(Prof. Lossen's) system of coloring and classify- 
ing THE ERUPTIVES ? 
Major Powell answers : " No." 
Dr. Hunt says : " Lossen's scheme for classifying eruptive 
rocks is defective : first, because it includes many rocks which 
are not plutonic ; and second, because it does not distinguish 
l)etween true plutonic rocks and those which are endogenous or 
are pseudo-plutonic, that is to say are softened and displaced 
crenitic masses." 
Prof. Le Conte : " I think any well-recognized scheme of 
colors is better than the present chaos. I like the scheme pro- 
posed by the International Congress. As to classification I don't 
like the term melaphyre. It is too indefinite." 
Prof. Irving : " I am not able now to refer to this classifi- 
cation, but as I recollect I did not like it." 
Dr. Emmons : " No." (In a previous letter, Dr. Emmons 
says on the subject of eruptive rocks : " Whatever the colors may 
be, I think it would be entirely futile for the Congress to recon- 
cile any system with the widely variant names employed by 
different petrographers of the present day, and this, in the pro- 
visional system adopted for the maps of Europe, seems to have 
been partially recognized." 
" This system, however, seems to me a purely arbitrary one, 
founded on no natural law, except as regards ' Present Erup- 
tives.' But who can determine beyond a doubt whether a recent 
lava is Quaternary or Pre-Quateruary, or why shall we distin- 
guish practically identical rocks by separate colors, because one 
happens to be eruptive before and the other after an imaginary 
period of time? It moreover seems of doubtful advisability to 
attribute the importance of being one of the seven great divi- 
sions of eruptive rocks to a material like serpentine, which is 
always the product of alteration of some other rocks or mineral, 
and probably quite as often of sedimentary as of eruptive rocks 
or minerals." 
" I would suggest three fundatnental colors, or distinct tones of 
a general color, be assigned to eruptive rocks. Of these, one 
should be given to crystalline or granitoid rocks, one to intrusive 
or porphyritic rocks, which have congealed slowly and under 
great pressure ; one to surface-flows, or rocks that have congealed 
