Characters of the Fisher Meteorite .— Winchell. 
175 
common orientation, and the lamellae themselves extinguish 
in unison and frequently parallel to their elongation. Occa¬ 
sionally a granule, not exactly in line with the series consti¬ 
tuting one of the lamellae, but rather between two lamellae, 
extinguishes at a different angle. The lamellae in the olivine 
chondri are nearly straight and parallel. Between them is 
sometimes an isotropic substance which is probably glass, but 
sometimes this substance affords an aggregate polarization. 
In those olivine chondri in which the lamellae are cut parallel 
to 001, that is, perpendicular to the mean axis of elasticity, 
the distinct cleavages run directly transverse to the elongation 
of the lamellae as viewed. Hence the lamellae are of the nature 
of plates parallel to 100. Sometimes the lamellae contain no 
interlamellar glass, but the alternate lamellae are differently 
oriented, there being two directions, with an angle of about 
24 degrees between them. Sometimes parts of different chon- 
drules are closely adjacent, each having its independent 
orientation. In this condition the appearance somewhat 
resembles the radiating lamellae of the chondrules of enstatite, 
and in some of the enstatite chondrules olivine constitutes a 
portion of the interlamellar mineral. 
There are apparently two isotropic substances in this 
meteorite, one being glass (at least glassy) and the other 
having a cleavage. The latter is clear as glass in ordinary 
light, and has refraction approaching that of olivine, as 
shown by the shagreen which is produced on lowering the 
condenser. It may be maskelynite, which is a mineral dis¬ 
covered by Tschermak in 1872, isotropic but having nearly 
the composition of labradorite. Below is a pencil sketch of 
the aspect of the cleavable grain in common light with the 
condenser lowered. This indeed is the only grain of the 
isotropic substance which J hqve been able to find 
^ showing a distinct cleavage. The non-cleavable 
substance, appearing like glass, is rather widely dis¬ 
tributed, but there is no certainty that they are the 
same, although the glassy substance seems occasionally to 
transmit a little light between crossed nicols. The cleavable 
mineral has occasionally a trace of a second cleavage as rep¬ 
resented. 
