THE ORIGIN OF IGNEOUS ROCKS. 
197 
into the geological occurrence and geographical distribution 
of igneous rocks, as well as more complete and systematic 
analysis of their chemical composition. Realizing the in¬ 
completeness of our knowledge of the chemical, mineralogi- 
cal, and geological relationships of igneous rocks, the writer 
cannot assume to have done more than call attention to their 
importance and point out the direction in which the future 
development of the science of petrology should be made. 
The confusion which has overtaken the classification of 
igneous rocks and the burden which is being heaped up by 
the present tendency to multiply its terminology by creating 
names for each modification of rock will find their remedy 
in a more logical conception of the true nature of the differ¬ 
ences of rocks and in a better understanding of the relation¬ 
ship between all of the rocks of a natural geological and 
geographical group. 
