264 Brush and Dana —the Spodumene of Branchville, Conn. 
them could not be answered; the whole gave the effect of 
aggregate polarization. The above statement is true for the 
greater portion of each of the slides—the result thus far was 
negative. 
Occasional irregularities, however, in the usually parallel 
fibrous structure, which may not inaptly be compared in appear- 
ance to the grain of wood-fiber in the bakadibprbved of a knot, 
as seen in a smooth board, gave better results. The fibers in 
such cases are much curved and irregular in outline, and so 
separated from one another that they are seen to be merely 
enclosures in a surrounding matrix. In other cases, this enclos- 
ing material forms open spots, where the structure (in polarized 
light) is found to be that of ordinary albite, and into this the 
needle-like fibers of the other mineral project (this is illustrated 
in fig. 15,a = albite). Still again, on the edges of the sections 
\ i \' \ 
; jj 
Y Y 
( Re \ r 
y i ( Ny ‘ 
\ | | \ \) 
Day \\ } 
y J 
/ q ( ff i ff ij 
| 2 } i 
! i | 
} ) a i 
where a degree of thinness impossible for the whole slide is 
sometimes attained, a similar satisfactory result is reached. e 
fibers in such cases are distinctly seen, independently of each 
other and of the enclosing albite. They are generally nearly 
straight and parallel, but not infrequently the shape is more or 
less irregular; branching forms recalling some kind of coralline 
