296 



2. On Superposition. By Professor Kelland. 



The object of this paper was to defend the method of demonstra- 

 tion employed by Euclid from some of the charges which have been 

 at various times brought against it. In particular, it was shown 

 that the method is not deficient in variety of demonstration of the 

 same fact. This position was illustrated by the exhibition of twelve 

 totally different demonstrations of the problem, " To cut three- 

 fourths of a square into four pieces which shall form a square.'' 



3. On the Colouring Matter of the Eottlera tinctoria. By 

 Professor Anderson, M.D., Regius Professor of Chemistry 

 in the University of Glasgow. 



The Rottlera tinctoria is a large tree which is found distributed 

 over the whole Indian peninsula, and is particularly abundant in the 

 hill jungles of Mysore, Canara, and Malabar. The fruit, which is 

 about the size of a pea, is covered with curious stellate hairs and 

 red glands, which are easily separated by rubbing, and form without 

 further preparation the colouring matter which is sold in the bazaars. 

 It is a perfectly uniform brick-dust coloured powder, which repels 

 water, and is scarcely soluble in that fluid. Alcohol and ether ex- 

 tract a red colouring matter, as do also the alkalies and their carbo- 

 nates. A proximate analysis showed it to contain — 



100-00 



The colouring matters consist of at least three different substances. 



1. A crystallizable matter extracted by ether, to which the author 

 gives the name of Rottlerine. It forms a mass of yellow crystalline 

 scales, having a fine satiny lustre. Insoluble in water, sparingly 

 soluble in alcohol, and readily in ether. It dissolves in alkaline solu- 

 tions with a deep red colour, but does not form definite compounds 

 with the metallic oxides. It is decolorized by bromine with the pro- 



