Vol. 6, 1920 PETROLOGY: G. P. MERRILL 459 
strong blast of hot air or steam into melted glassy furnace slag, it is blown 
into spray, and usually gives rise to pear-shaped globules, each having 
a long, hair-like tail, which is formed because the surrounding air is too 
cold to retain the slag in a state of perfect fluidity. Very often the fibres 
are of the chief product. I have never observed any such fibres in me- 
teorites. The formation of such alone could not apparently occur unless 
the spray were blown into an atmosphere heated up to near the point of 
fusion, so that the glass might remain fluid until collected into globules. 
The retention of a true vitreous condition in such fused stony material 
would depend on both the chemical composition and the rate of cooling, 
and its permanent retention would in any case be impossible if the original 
glassy globule were afterwards kept for a long time at a temperature 
somewhat under that of fusion. The combination of all these conditions 
may very well be looked upon as unusual, and we may thus explain why 
grains containing the glass are comparatively very rare; but though rare 
they point out what was the origin of many others. In by far the greater 
number of cases the general basis has been completely divitrified, and the 
larger crystals are surrounded by a fine-grained stony mass. Other grains 
occur with a fan-shaped arrangement of crystalline needles, which an 
uncautious, non-microscopical observer might confound with simple 
concretionSc They have, however, a structure entirely different from any 
concretions met with in terrestrial rocks, as for example that of oolitic 
grains. In them we often see a well-marked nucleus, on which radiating 
crystals have been deposited equally on all sides, and the external form is 
manifestly due to the growth of these crystals. On the contrary the 
grains in meteorites now under consideration have an external form 
independent of the crystals which do not radiate from the centre, but from 
one or more places on the surface. They have, indeed, a structure abso- 
lutely identical with that of some artificial blowpipe beads which become 
crystalline on cooling. With a little care these can be made to crystallize 
from one point, and then the crystals shoot out from that point in a fan- 
shaped bundle, until the whole bead is altered. In this case we clearly 
see that the form of the bead was due to fusion, and existed prior to the 
formation of the crystals. The general structure of both of these and the 
previously described spherical grains also show that their rounded shape 
was not due to mechanical wearing. Moreover, melted globules with well- 
defined outline could not be formed in a mass of rock pressing against them 
on all sides, and I, therefore, argue that some at least of the constituent 
particles of meteorites were originally detached glassy globules, like drops 
of fiery rain." In this Sorby would appear to have had reference only to 
kugels with radiate, internal structure. 
Tschermak, who together with Haidinger, was one of the first to pro- 
nounce on the tuff -like character of the chondritic meteorites, announced 
in 1874^*^ the opinion that the individual chondrules (kugelchen) were but 
