458 
PETROLOGY: G. P. MERRILL 
Proc. N. a. S.- 
they can, except as noted below, have little bearing upon the subject of 
the origin of the chondrules themselves. They are, therefore, passed over 
for the present. 
THK ORIGIN OF THE CHONDRUIvE 
I. Theories of Origin, — In this review it will perhaps not be necessary 
to go back much beyond the time of the introduction of the microscope 
and thin sections into the study of rock structures since obviously little 
that was accurate could be told of them by the naked eye alone. 
A brief glance at the literature is sufficient to suggest that many of the 
opinions expressed have been based upon examinations of but a limited 
number of occurrences which quite failed to yield the information neces- 
sary for building satisfactory hypotheses or conclusions. 
Reichenbach, as early as 1860^ wrote, "Aus allerdem wird es klar, das 
die Einschlusse in den Meteoriten, als die Triimmer und die geschicbartigen 
Knollen und Kugeln darin, keine einfach nachen Bestantheile, sondern 
nichte anderes sind als auch wie die Meteoriten. Meteoriten nur von 
anderer Anordung ein und derselben naturn Bestandtheile " And again, 
"Es sind also die Einschlusse theils kleine meteoriten, theils Triimmer von 
meteoriten von hohenen Alter als diejenigen meteoriten es sind, in welche 
sie eingeschlossen vorkommen ; es sind altere kleinere meteoriten in junger- 
ern grossern meteoriten." In brief, and in plain English, he believed each 
particle as now found to represent a minute but independent meteorite 
derived from the breaking up of some older preexisting stone and now 
included as a constituent part of one new formed. 
In discussing the microscopic structure of meteoric stones, H. C. Sorby, 
in 1864, wrote, ^ "It would, therefore, appear that, after the material of 
the meteorites was melted, a considerable portion was broken up into 
small fragments subsequently collected together, and more or less consol- 
idated by mechanical and chemical action. * * * Apparently this break- 
ing up occurred in some cases when the melted matter had become crys- 
talline, but in others the form of the particles lead me to conclude that it 
was broken up into detached globules while still melted. This seems to 
have been the origin of some of the round grains met with in meteorites; 
for they occasionally still contain a considerable amount of glass, and the 
crystals which have been found in it are arranged in groups radiating from 
one or more points on the external surface in such a manner as to indicate 
that they were developed after the fragments had acquired their present 
spheroidal shape." In continuation of this same idea in 1877,^ Sorby 
wrote: "As is well known, glassy particles are sometimes given off from 
terrestrial volcanoes, but on entering the atmosphere they are immediately 
solidified and remain as mere fibres, like Pele's hair, or as more or less 
irregular laminae, like pumice dust. The nearest approach to the globules 
in meteorites is met with in some artificial products. By directing a 
