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Literature,” from which we extract the following passages 
bearing on the use of the microscope: 
“English petrography does not exist; what we have in its 
stead is an indefinite obsolete grouping of rocks patched up 
with occasional borrowings from the Continent. And yet, 
strange to say,it is in England that the most important steps 
in modern petrography has originated. Sorby’s application 
of the microscope to the study of rocks has opened a new era 
in the science, and our good friend Sorby himself is regarded 
as a kind of demi-god in the eyes of our German brethren of 
the hammer. 
“The great paper of Mr. Sorby published here thirteen 
years ago has done much to quicken research by showing 
that the older methods were in many respects untrust- 
worthy. ‘These methods were based primarily upon che- 
mical analysis. But such analysis, while it reveals the 
ultimate chemical constitution of the rock, may not ex- 
plain its mineralogical composition. The various siages 
of the metamorphism of the component minerals are thereby 
often lost sight of. Hence two rocks, having by analysis 
approximately the same chemical composition, may differ 
materially from each other in mineralogical composition. It 
is here that, as Sorby showed, the microscope comes in to 
our aid, and shows what the different mineral ingredients of 
the rock are, how far they have respectively undergone altera- 
tion, how they are built into each other so as to form the 
rock-mass, and under what conditions they may originally have 
been formed. ‘This important addition to the methods of 
research has so powerfully affected petrography, that this 
branch of science must be regarded as at present in a transi- 
tion state. 
* Among the Continental petrographers who have led the 
way in the recent reform and extension of this branch of 
science, none can claim a more prominent place than Dr. 
Zirkel. Although still a young man, he has held professor- 
ships successively at Lemberg and at Kiel, and we rejoice to 
hear from him that he has been selected to succeed the vene- 
rable Dr. Naumann at Leipzig. He is the author of many 
excellent mineralogical and petrographical papers, and of the 
best text-book of petrography which has yet been published. 
Especially has he distinguished himself by the zeal with which 
he has followed out the ideas first broadly sketched by Mr. 
Sorby, and has shown how absolutely indispensable is the 
application of the microscope to the study of the composition 
and history of rocks. His researches, while extending over 
the length and breadth of Germany, have not been confined 
