4 WM. H. HOBBS 
observations of other but similar cases of magmatic differentiation. 
It is now the exception rather than the rule to discover an 
igneous rock mass of considerable dimensions in which some 
evidence of such gradations may not be observed. 
The introduction of the petrographical microscope and its 
accessories, bringing as it did quick and delicate methods for 
determining the mineral constitution of a rock, naturally enough 
drew away the attention of petrographers from the slower and 
less brilliant methods of chemical analysis, which up to that 
time had been almost the only ones in use. Moreover most of 
the analyses of the period were, as we now know, inaccurate and 
failed to show the real chemical differences between individual 
rocks. The multiplication of the number of analyses and the 
improvements in the methods of rock analysis which have been 
made during the last decade, particularly by Hillebrand, have 
disclosed important differences among rocks formerly classed 
together, and thus necessitated a considerable elaboration of the 
systems of classification. 
With this elaboration rock names have been introduced into 
the science with a rapidity which is little short of bewildering. 
The older petrological nomenclature was largely binomial or 
polynomial (2. e., mica-syenite, quartz-mica-diorite) though the 
recent names seem planned for a monomial nomenclature (7Z. @., | 
ciminite). It is therefore not strange that misunderstanding has 
arisen in some quarters, where it is not realized that the new 
names proposed are for the most part specific and varietal in 
their nature and in no way to be correlated with the great family 
names such as granite or gabbro, and hence a protest has been 
made against what seems a needless overburdening of the science 
with names. Without entering upon this question here it may, 
I think, be stated with all assurance that some reforms are 
imperatively demanded before the worker will be fully equipped 
to discover the relationships among rocks because of the incubus 
of unclassified facts by which the science is now encumbered. 
Some of the particular reforms which to me seem desirable and 
practicable will be briefly described. 
