XXXVI. ABSTRACT OF PROCEEDINGS. 



and other leaves, but they are inferior in starting fermen- 

 tation. Indican, the glucoside yielding indigo blue can be 

 extracted from the dried woad leaves by ether, on washing 

 this with water and evaporating the water solution the 

 indican is left as a pale brown syrup, soluble in spirit, 

 ether, etc. Indican is very unstable, boiling or long heat- 

 ing its solution decomposes it and it yields indiglucin but 

 no indigotin, i.e., indigo blue when treated with acids. 

 To illustrate the process of dyeing with woad ; digest half 

 a pound of woad with a gallon of water, in a closed vessel, 

 at 100° F., for 12 or more hours ; then stir in about \ oz. of 

 lime. The indican (C 26 H3iNO ]7 ) undergoes hydrolysis and 

 indigo- white is formed. If now a skein of white wool be 

 placed in the liquid for an hour or so, on taking it out and 

 exposing it to the air it will acquire a pale blue colour ; 

 the soluble indigo- white hydrindigotin(0 16 Hi 2 N20 2 ) or reduced 

 indigo is oxidised by the air to insoluble indigo-blue or 

 indigotin (O 16 H 10 N 2 O 2 ). 



An interesting account of the preparation and use of 

 woad from the pen of Dr. C. B. Plowright, will be found in 

 " Nature" of 1st February, 1900. 



Remarks were made by Mr. W. A. Dixon and Mr. Maiden. 



The experiment with Dr. Quaife's Lantern Electric Lamp 

 was unavoidably postponed. 



Mr. S. Henry Barraclough exhibited the Tantalum 

 Lamp with stereoscopic photographs of Clarke Maxwell's 

 Thermodynamic surface. 



Mr. H. A. Lenehan, showed various diagrams of modern 

 astronomical instruments for eclipse observations. 



