1082 The American Naturalist. (December, © 
=64.2% ; Magnetite=26.8% ; Iron oxides=6.9% ; Siliceous products 
=2.00%. 
Miscellaneous.—In the abstract of a paper read before the Geo- 
logical Society of America, E. B. Mathews® gives a brief account of 
several distinct types of granite, covering an area of 900 square miles, 
in the Pike’s Peak district, Colo. All are believed to be portions of a 
single magma, erupted at different times, with the later portions cut- 
ting through the earlier ones. 
Bayley’ records the existence of a series of acid and basic tuffts, 
amygdaloids, glassy and crystalline lavas, and spherulitic phases of 
volcanic rocks on North and Vinal Haven, Maine. 
Darton and Kemp,’ in the same brochure describe a dyke near De- 
wĦt centre, three miles east of Syracuse, N. Y. It is a peridotite simi- 
lar to that described by Williams from Syracuse. Its composition is 
represented by the following figures : 
SiOz i s se ~ mo Nio CaO BaO SrO Mgo K}0 NaO P.O; ve SO; S H,O Total — 0 =S 
36.80 1.2 .09 8.63 .12 tr 25.98 2.48 17 .47 2.95.06 .95 7:44—100.22—.471—=99.75 
Lepsius’ divides gneisses into meta-gneisses—those formed by the 
metamorphism of sedimentary rocks, pro-gneisses—those constituting 
portions of the original earth crust, gneiss-granites—those produced 
from granite by fluidal movements of a liquid rock magma—and 
clasto-gneisses, those formed by the crushing of a solid granite. 
Hornung’ has examined a series of rocks associated with the mela- 
phyres in the South Harz, and has shown that some of those that have 
been called clay slates are in reality volcanic tuffs. Their material 
was erupted in two different periods, and both were erupted before the 
melaphyre. The older tuff is composed essentially of a green basic 
pumiceous glass, the second of splinters of biotite, zircon, quartz, plagi- 
oclase, pyroxene and red garnet. Both have the typical tufaceous 
structure. The tuffs are interbedded with sediments, and their mate- 
rial is more or less thoroughly intermingled with the material of these 
latter rocks. 
In the District of Columbia granitic rocks” have disintegrated into 
Š Bull. Geol. Soc. Amer., Vol. 6, p. 471. 
*Ib., p. 474. 
1 Ib., p. 477. 
* Notizbl. des Ver. f. a iv foes 15 Hft., p. 1. 
* Min. u. Petrog Mitth., xiv, p. 283 
1 Merrill, Bull. Geol. i Soe, pera Vol. 6, p. 321. 
