1889-90.] Mr C. Michie Smith on Absorption Spectra. 
127 
Kamala and Waras have been examined by Mr D Hooper,* who 
shows that they are very similar, but not identical. 
It is worth noting that of the colouring matters examined those 
giving definite absorption bands yield fugitive dyes, while the others 
yield permanent dyes. 
My thanks are due to Dr J. Gibson for assistance received during 
the progress of the inquiry. 
Description of Plate. 
(a) Colouring matter from Trichosanthes palmata, 0’5 cm. thick. 
(b) ,, „ 2-0 cm. „ 
(c) „ ,, 4*0 cm. „ 
(d) Chlorophyll from cabbage, 2 cm. thick. 
(e) Colouring matter from Trichosanthes palmata + ammonia sulphide after 2 days. 
(f) „ „ „ 11 „ 
(d) >> ” » 39 ,, 
(h) Chlorophyll + ammonia sulphide. 
(i) Colouring matter from Trichosanthes palmata + hydrochloric acid. 
(j) Chlorophyll + hydrochloric acid. 
(Ic) Colouring matter from Ventilago madraspatana, thin layer. 
( l ) , , , » thick layer. 
(m) ,, funiculus of “W attle. 
(n) Waras. 
(o) Kamala. 
On a Mechanism for the Constitution of Ether. 
By Sir William Thomson. 
(Read March 17, 1890.) 
1. In a communication to the Royal Society of Edinburgh of 
4th March 1889, I stated the problem of constructing a jointed 
model under gyrostatic domination, to fulfil the condition of having 
no rigidity against irrotational deformations, and of resisting rota- 
tion, or rotational deformation, with quasi-elastic forcive in simple 
proportion to rotation. I gave a solution, illustrated by a model, 
for the case of points all in one plane ; but I did not then see any 
very simple three-dimensional solution. After many unavailing 
efforts I have recently found the following. 
* Pharmaceutical Journal, vol. xviii. p. 213. 
