334 Mr Herschel on the Deviations from Newton's scale 
who carried the holy and eternal principles of religion not on his 
lips, but in the inmost feelings of his heart, from whence they 
emanated in actions which pervaded and ennobled his whole 
being and conduct. 
Art. XIII. — On certain remarkable Instances of deviation 
from Newton's Scale in the Tints developed by Crystals with 
one axis of Double Refraction , on exposure to Polarized Light. 
By J. W. Herschel, A. M. F. R. S. Lond. & Edin. and 
of the Camb. Phil. Soc. (Concluded from VoL IV. p. 344.) 
J3lJT the structure of the crystal under examination is yet 
more compounded than what I have been describing. Dr 
Brewster has already, in a highly interesting paper in the Edin- 
burgh Transactions *, described the union of our first variety of 
apophyllite with another, possessing two axes of double refrac- 
tion, forming regular columnar crystals, consisting of an interior 
portion of one kind, surrounded by a case or border of the other, 
&c. The specimen I am now describing, however, presents the 
hitherto unique combination of no less than three distinct sub- 
stances, having each but one axis of double refraction, uniting 
to form a single crystal, and following regular geometrical laws 
of juxtaposition. In examining the two plates as above detail- 
ed, the portions most transparent and uniform in their structure 
were selected, and insulated from the rest, by fastening them 
over holes of about an eighth of an inch in diameter in sheets of 
lead. But when the whole plates were exposed to a polarized 
beam, each was observed to consist of two distinct portions or 
compartments, as represented in Plate VII. Fig. 3. where the 
interior parts abcde are those already examined ; the border 
ABC deb a being separated from the inner portion by a plane of 
junction which, in the thicker plate, appeared, on inclining it, to 
be marked with a series of pretty broad coloured fringes, whose 
origin is sufficiently obvious. Considerable irregularity appear- 
ed in the structure of this border, but, at a perpendicular inci- 
* This paper is printed in this Journal T vol. i. p. 1, and never appeared in the 
Transactions.— 
