1892.] Mineralogy and Petrography. 611 
concludes that these bodies are not inclusions torn from a deep-seated 
basic rock as is sometimes thought, but that they are concretions of the 
basic minerals of the basalt, formed during the intratellurial period of 
its magma’s history. Another interesting feature of the Stempel 
occurrence is the abundance and variety of true inclusions found 
therein. These are limestone, quartz, feldspar and amphibolite frag- 
ments and others torn from a cordierite rock. The limestone has pro- 
duced but little effect upon the surrounding rock other than rendering 
its texture coarser by increasing the size of its feldspathic constituents. 
The limestone itself has suffered little change. The quartz fragments 
are all surrounded by rimsof green augite crystals, and in their inter- 
ior they are filled with swarms of cavities either empty or filled with 
liquid. Sandstone inclusions now consist of grains of quartz, cemented 
by a glass that has originated in the fusion of the cement of the origi- 
nal rock. This glass sometimes contains trichites and magnetite grains, 
when it is colorless; sometimes it is devoid of them and is colored 
brown. The glass cement also frequently contains drops of glass that 
differ from the enclosing material in that it dissolves readily in hydro- 
chloric acid, while the latter is unaffected by this reagent. The inclu- 
ded substance is regarded as the pure glass produced by the solution 
of the cement of the sandstone, while the insoluble variety is that to 
which silica has been added by the corrosion of the quartz grains. 
The finer grained sandstones have yielded basalt-jasper. In their 
glassy constituent are numerous crystals of apatite that are similar in 
most of their properties with the nepheline and cordierite crystals 
observed by Zirkel in some of the basalt-jaspers described by him. 
The orthoclase inclusions are penetrated by tiny veins of glass. Both 
the feldspar and the glass contain small violet octahedra of some 
spinel and blue pleochroic needles of glaucophane, while tridymite 
plates occur in the latter substance. An aggregate of orthoclase and 
ioclase contains flecks of green glass between the grains that is 
thought to be fused mica, while the feldspar is filled with sillimanite 
needles. The other inclusions present features that are worthy of 
notice, but they cannot be described in the present place. The article 
will well repay the reader for its perusal. 
The Crystalline Rocks of Tammela, Finland.—The archean 
rocks in the vicinity of Tammela, in the South-western part of Fin- 
land, are crystalline schists, granites, gabbros, porphyrite and vitro- 
phyres. A gray granite, Sederholm’ thinks, is closely related to the 
1Min. u. Petrog. Mitth., xii, p. 97. 
