Memoirs presented to the Cambridge philosophical society on the occasion of the jubilee of Sir George Gabriel Stokes, bart., Hon. LL. D., Hon. SC. D., Lucasian professor.

C(m bridge.1P/zilosoprziclt Transactions, -'o1. X VI, Plate 3.
PmLATES 3 -23 IL.LUST.RATI:NG ProFseso IVEINfL S PAPER (p3p 298-315, On th e
effects of Dilution, mnTempaturer aad otheî cireicnmstacnces, on the A bsorption zStpectra -tf
so/ttio-rns of Dicidyniuwn antid ]Zriu salts.?These plates a-re ail:repodutio enlarged tco double the size, of photographs of some
of the spectra friom. which the conlu-etsions in. the text have been deduced. In the
processes of enlarlgelnent and:ireproduiction soma of the lf inter dlet ails visible in the
original negatives have (perhaps una voidably) been l ost: but they present the salient
features of the' changes in -the spectra piodl uced by t;he variations of cirCemnstance
Tihe references to thlse plates 1in the text applied tlo -lthe original negatives and
were printed before the rleproducti;ns were reaf d t he ]lc la.tt er, being postivoes.i, tare
reversed, and:i orderit t-i it lh references may be easily i:nt eligible it haLs been
necessary fto place thé red cu-l tds o:f te spectra on the left htan.d
UThe figures at the t-opt of each plate tre the approximate wave lengths of tthe
bands in. t?é spectra benealith tle:, an:. sl.ficiently indicate thie range uotf[ tle spetruil
ph.'totogrraphed.
PLATE 3.
Absorpltionls of solutions o:f didyuini chlloride, i- four degrees of dilution inl tiiacknesses inversely;as the d(iluti-ons. 'lThi ost concenxltrae ated solution contained 1t40-7 g;ra.s per litre, an.d the absorbent
thickness of t his solution was 38 min. —
î^'~~~. Ti s.uon S C s tre g tl
-i strongest t so lut on
- --.....i ~ seolutioz-i 1/4 strenigtl
i3i5iiii lo;i 152'5 min. [hink
M ~ '"" solution 1/2 stirengh
2-: 760f mini. lhick
I:t wi ll. be n-oticed how very nea erly identical these four spectrat aie. r -The original. photograph
shews a number of fziint antllds which have not comne ont inl thle reprodiuctiuon They re however as
nearly identical ini all four spectra as arae the stronger lands here reproduced.