266 The American Geologist. November, igoo 
currences noted are all of questionable character and may per- 
haps be composed instead of a liquid of low index of refraction. 
II. Liquid inclusions. 
1. Along curving planes. Liquid inclusions are not com- 
monly found along planes of any sort, but when found thus 
they are abundant. Their size varies markedly even along a 
single plane; instead of disappearing abruptly, they become 
smaller and smaller, but at the same time more and more nu- 
merous, as one approaches the limit of the plane. Thus the 
total amount of liquid (or liquids) enclosed probably remains 
about the same. More frequently, they are invariably very 
small along a given plane. The smallest liquid inclusions are 
always spherical, but the larger ones, while generally roughly 
spherical, may vary to shapes the most irregular. Very rarely 
they show rectilinear outlines, which are doubtless impressed 
upon theui by the enclosing feldspar. All, except the very 
smallest, commonly contain solid inclusions; the smaller ones 
contain only one or two, while the larger ones usually contain 
several, and may show as many as thirty or forty. These solid 
particles never show any arrangement in the liquid, though 
they seem tO' invariably adhere to the surface of the surround- 
ing mineral. Occasionally the larger cavities of the feldspar 
contain two liquids, one inside of the other. And indeed it is 
easy to distinguish two liquids in different cavities, since the 
ordinary one gives a marked relief, while another, occurring 
much more rarely has an index of refraction nearly as high 
as that of the feldspar, and the relief is scarcely perceptible. 
2. Throughout the feldspar. The liquid inclusions which 
are scattered broadcast throughout the feldspar are usuall}' 
always of extremely small dimensions. More rarely they also 
occur of larger size; when small they are roughly spherical, 
but when they become larger they usually lose all regularity of 
shape; like those occurring along planes they often contain 
black solid inclusions, which, however, have never been ob- 
served in such numbers as in the larger inclusions along the 
planes ; they are usually limited to one or two. 
III. Solid inclusions. 
I. Along curving planes. These inclusions have already 
been mentioned as occurring within the fluid inclusions. That 
is their ordinary habitat, but they occur also, though more 
