450 
PETROLOGY: G. P. MERRILL 
Proc. N. a. S. 
the term chondren, though in his plate legends and descriptions he desig- 
nates both as Kugelchen, thus using the two terms synonymously. 
A perusal of the literature shows that by English and American writers, 
the terms chondrule, chondrus, chondrum or chondros are now and have 
for some years been applied to the rounded and oval granules presenting 
a considerable range in mineral composition and still wider range in in- 
ternal structure, thus making the terms synonymous with kugel or ku- 
gelchen as used by Tschermak above. Of later years and as illustrated 
in the generally adopted scheme of classification,^ there has seemed a dis- 
position to use the term kugel in a descriptive adjective sense, as kugelchen 
ckondrit, under which name are included stones containing chondrules 
(or chondri) having a radiate structure — the spherulitic^ chondrites of 
American writers. There has thus apparently arisen in the minds of 
many a confusion which, as it seems to the writer, has been in part at 
least responsible for the diverse views expressed concerning the origin 
of these peculiar bodies. In other words, there has been a failure to recog- 
nize or discriminate between the kugelchen with radiate structure and the 
often irregular polysomatic forms with the "uneben Bruche." 
The present paper, then, represents an attempt on the part of the author 
to make this discrimination and to show how far proposed theories may 
apply to the various forms presented. 
NATURE OF THE CHONDRULE 
At the outset and for the purpose of making clear what is to follow, 
it will be well to figure and describe a few characteristic forms of the indi- 
vidual chondrules. This notwithstanding the previous most excellent 
and comprehensive work of Tschermak and Cohen. ^ 
Mineralogicalty, the chondrules, using the word in its broadest and 
most comprehensive sense, in nearly all meteorites are composed chiefly 
of the minerals olivine or pyroxene, the latter in either orthorhombic or 
monoclinic forms, or both. Some are largely of an undifferentiated glass. 
Feldspars occur but rarely except in the form known as maskelynite. 
In addition are occasional enclosures of metal or metallic sulphides, chro- 
mite or other minor constituents. The metallic iron sometimes occurs 
in rounded chondrite-like blebs, though it is doubtful if this should be 
referred to under that name. Structurally, the chondrules in the same 
meteorite may vary from densely cryptocrystalline, almost amorphous, 
to those that are part glassy and porphyritic or even holocrystalline. 
I. Glassy, Cryptocrystalline and Radiated Forms. — In figures 1 and 2, 
are shown examples of cryptocrystalline forms from the stones of 
Barratta, Australia, and CuUison, Kansas. That of figure 1 is of a peculiar 
brownish translucency and very dense, resembling the "felsitic" structure 
of the early petrologist. In the Cullison stone, figure 2, the chondrules, 
also of a brownish color, are not completely isotropic but between crossed 
