PETROLOGICAL ABSTRACTS AND REVIEWS 85 
Vulcanism is defined as that phenomenon by which juvenile materials 
are brought from the interior of the earth into or upon its crust. These 
materials are divided into three groups: ‘‘rheumatitische” (fedya, 
to flow), or that material which was poured out in a molten condition, 
“klasmatitische” (kAaopa, broken, fractured), material that is angular, 
broken, or rounded, and ‘“pneumatolitische,”’ or gaseous material. 
Since observations of eruptions cannot always be used in determining the 
history of a volcano, a morphological, topographical, geologic, petro- 
graphic, chemical, and physical study of previous eruptions must be 
made of former lava flows. The author gives his objections to the 
application of local for specific names for certain phenomena, as is done 
in the nomenclatures of Seebach and Stiibel. 
The most striking feature of a volcano is its built-up cone, and it is 
upon a study of the various characteristic forms which may be easily 
correlated with ideal sections, and upon a study of the materials which 
built up these cones, and of the forces which produced them, that the 
safest and most positive classification can be built. Too little regard, 
says the author, has heretofore been paid to “klasmatitische”’ material 
and he proposes a classification based upon the forms of the hill produced 
by the erupted material. Yet the author’s own statement that the 
klasmatitic material may become the sport of the wind or be carried 
off by rainfalls shows how the outlines of a volcano may be altered to a 
remarkable degree in different latitudes. This would invalidate the 
classification to some extent, for it is, after all, based upon the topo- 
graphic forms produced by the materials not carried away. Neither 
does the classification take into consideration the gaseous emanations 
upon which the character of an eruption somewhat depends. 
Seven different types of volcanoes are recognized according to size, 
structure, and form. 
“Pedionites” are characterized by the great extent of their lava 
flows. No volcano of this type is known for certainty in historic times. 
The material is generally rheumatitic though some klasmatitic is found. 
The Deccan is an example of a pedionite. 
‘““Aspites”’ are characterized by bases which are wide in proportion to 
their height. They usually have a crater on the summit and the material 
is generally rheumatitic. Mauna Loa is an example. Vesuvius is a 
pseudoaspite. 
“Tholoides”’ have slopes of over 35° and are convex upward. Like 
the preceding, the material erupted is rheumatitic but the height of the 
cone is greater in proportion to its base. This form is characteristic of 
