70 The American Naturalist. [January, 
of these two little-known rock groups. He has discovered that the 
scapolite rocks are sometimes the result of contact phenomena in 
marbles. Sometimes they are the result of the alteration of gabbros, 
and sometimes they are original. In every case it is found that there ` 
is a tendency of the rock to possess as constituents one or more rare 
rock-forming minerals. As the writer has examined all these very 
carefully, his paper is a mine of wealth to the petrographer who has 
to deal with rare minerals. Among the most interesting observations 
described may be mentioned the existence of dumortierite and cordier- 
ite in a gneiss from Bamle, Norway; fuchsite in a mica-schist from 
Salem, India; and the new mineral fouquéite in a gneiss from the 
same vicinity. Original epidote and parallel growths of this mineral 
with allanite in a pyroxene gneiss from Morbihan, France, and in a 
scapolite gneiss from Odegarden, Norway, are described, as are also the 
regular arrangement of rutile needles in phlogopite and garnet and 
micropegmatitic intergrowths of pyroxene and quartz (page 297),PyTOX- 
ene and oligoclase (pp. 316-318), garnet and quartz (p. 317); and 
amphibole and oligoclase (p. 319). The varieties of feldspar known 
as sun-stone and esmarkite are referred to, the properties of the min- 
erals of the scapolite group are discussed, and the occurrence of 
secondary and original wollastonite and wernerite is mentioned. 
Contact rims consisting of hypersthene and amphibole, and tremo- 
lite and amphibole, are pictured around olivine in olivine-gabbros, 
and a rim consisting of biotite and amphibole is figured as seen aroun 
ilmenite. In addition to the observations made by Lacroix, there are 
incorporated in the paper descriptions of the facts discovered by earlier 
workers in the domain of these rocks. It therefore becomes a valuable 
compendium of our knowledge of scapolite rocks, so far as known. 
In connection with his description of the New York rock, Lacroix 
gives an interesting account of the properties of the minerals found in 
the neighborhood of Pierrepont.——Mr. J. P. Iddings 4 has just pub- 
lished one of the most interesting papers that has yet appeared on the 
subject of lithophyse. The article opens with a description of the 
macroscopic structure of the great mass of obsidian known as Obsidian 
Cliff, in the ¥ellowstone National Park. The most striking feature of 
the southern portion of the mass is its perfect columnar structure, wi 
the columns all perpendiculag to the surface over which the rock 
flowed. A petrographical description of the rock follows, and it 15 
in this portion of his paper that the author shows well his ability to 
treat a complicated subject. Spherulites and lithophyse are minutely 
* Seventh Ann. Rep. Direct: U. S. Geol. Survey, p, 255 
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