Dr Stark on the Injlumct of Colour on Odours. 91 



were mixed up with a solution of gum-arabic, and laid on the 

 cards as equally as possible with a camelhair pencil. 



6. Pieces of card of equal size being coloured as mentioned 

 with various preparations of lead, viz. red, brown, yellow, and 

 white, and previously weighed, were exposed to the vapour of 

 camphor in the vessel before described. After exposure for some 

 time, and when cool, it appeared on weighing, that the 



Red had gained 1 grain in weight. 



Brown . . ^% of* a grain. 



Yellow . . y's 



White . . a trace. 



The whole of the upper surfaces of the red, brown, and yellow 

 cards were covered with a fine light downy deposit of camphor. 

 The white had an extremely fine deposit on its surface, but inap- 

 preciable by a very fine balance. 



7. Another experiment with cards coloured black, red, brown, 

 yellow, and white, exposed to the vapour of camphor, gave the 

 following results : 



8. In a similar experiment with cards coloured black, dark- 

 blue, dark-brown, orange-red, and white, the attractive powers 

 were as follow : 



of a grain. 



In all these experiments, it was invariably found that the 

 black attracted most, the blue next ; then followed the green and 

 red ; after these the yellow and white. The heat was never con- 

 tinued so long as to warm the apparatus, else the whole cam- 

 phor would have been driven oflP*. Neither was such a quantity 

 of camphor used as would have given a thick coating to the 

 substances employed, as then the attraction of the coloured 

 surfaces might have been diminished. 



