METEORITE COLLECTION—HANDBOOK AND CATALOGUE, 27 
The principal objection to the first view, pointed out by Wads- 
worth, is that fragments of pre-existing rock ought to show the con- 
stitution of the rock as a whole instead of a specialized structure. 
That to the second, pointed out by Merrill* inthe case of the San 
Emigdio meteorite at least, is that the great variety of forms under 
which the minerals of a single stone often appear, make it impossible 
to conceive of them as crystallizing from a single magma, 
It is evident that no positive answer can be given to the question 
as yet and it may be that the conditions under which the various 
structures have been produced have been essentially different. 
The matrix or mass of the stone in which the chondri are imbed- 
ded is usually made up of consolidated mineral splinters such as 
might have been produced by the breaking down of the chondri them- 
selves. It is occasionally, however, of a glassy or amorphous nature. 
The structure of aerolites not chondritic is frequently brecciated 
(Weston, 223, Taborg, 335) i. e.,made up of rock fragments cemented 
together, while others seem to have undergone metamorphism subse- 
quent to their consolidation (Chantonnay, 232). 
Evidence of physical change subsequent to consolidation is given 
by the s/ckenszded surfaces observable in many meteorites (Linn Co., 
255, Kesen, 267, Bath, 351). 
These are smooth, polished surfaces seen in different portions of 
the mass and are analogous to those found along faults in terrestrial 
rocks. They indicate a slipping or gliding of one portion of the rock 
on another after it had become cooled and solidified. | 
In the Puquios meteorite, which has a mass wholly metallic, a 
distinct faulting was observed by Howell. As some of the Toluca 
irons were found to become extremely friable on heating, it is prob- 
able that this faulting might have taken place during the passage 
of the mass near the sun or some other hot body. 
Veins are found penetrating the mass of many meteorites (Char- 
sonville, 230, Waconda, 310, Mocs, 323). These are frequently filled 
with metal (Schdénenberg, 254, Washington Co., 327, a) and in this 
case may have been produced as suggested by Preston by flowing of 
the molten metal into fissures made by cracking of the mass during its 
passage through the air. Others, however, contain opaque, graphitic 
or amorphous substances which probably segregated previous to the 
entrance of the meteorite into the earth’s atmosphere. 
A class of meteorites in the formation of which igneous agencies 
could have played little part are those known as carbonaceous. ‘These 
are black, very friable bodies having a specific gravity not over 2.00 
*Proc. U. S. N. M. No. 11, 1888. 
