SSB Mr Herschel on the Deviations from NewtorCs Scale 
cal phenomena of a maximum taking place between the extreme 
limits of the spectrum. I was led by this to conceive the pos- 
sible existence of bodies, in which the law of proportional action 
should be so far subverted, as to render the periods performed 
by a red ray, within their substances, actually shorter than those 
passed through by a violet one ; but certainly did not expect to 
find my conjecture almost immediately verified in the striking 
manner I am now to detail, and on the very substance which 
first gave rise to it. 
By the kindness of my friend Mr Lowry, (to whose liberality 
in rendering his invaluable collection accessible to scientific exa- 
mination, I have every reason to bear honourable testimony,) I 
was provided with a very large, and indeed splendid crystal of 
Fish-eye stone, which, though not very transparent, owing to air 
included between its laminae, was yet sufficiently so to exhi- . 
bit the rings of one axis with perfect distinctness, especially af- 
ter a few days'* immersion in oil of turpentine. The character 
of these rings was, however, altogether different from that of the 
rings exhibited in the ordinary variety ; their tints, instead of be- 
ing alternately white and black, with a little intermediate sha- 
ding of lilac and greenish-yellow, as described by Dr Brewster, 
being those of the following Table, in which the colour of the 
extraordinary pencil only is given. 
TABLE I. 
2st Order. Black, ruddy or yellowish-white, while, feint hlue, violet. 
2d Order, Indifferent pink, orange-yellow, dilute imperfect green, blue, purple. 
3d Order. Good pink, orange-yellow, tolerable green, blue, purple. 
4th Order. Fine pink, yellow, green, light blue, indifferent purple. 
5th Order. Rich pink, yellow, bhiish-green, indifferent purple. 
6th Orden Pink, pale yellow, pale green, 
'J'th Order. Pink, whitish, pale green. 
8th Order. Pale pink, whitish, pale green. 
9th Order.. Ditto, ditto. 
10th Order. Very pale pink, very pale green. 
11th Order. Extremely pale pink, extremely pale green, 
12th Order. Scarcely perceptible pink and green. 
In this series, the less refrangible rays evidently perform their 
periods with greater rapidity than those of the opposite end of 
the spectrum, but the number of alternations is still pretty con- 
