4 Shells as evidence of the Migrations. 
A very curious fact concerning this dye, which was 
noted also to some extent by the ancients, is the trans- 
formation through which it passes on exposure to 
sunlight. The fluid is at first colourless, but on exposure 
to the action of the sun it becomes of a bright yellow, 
speedily turns to a pale green, and continues to change 
imperceptibly until it assumes a bluish cast and thena 
purple red. These changes of colour, which are faster or 
slower according to the intensity of the sun’s light, are 
accompanied by the production of a disagreeable foetid 
odour, similar to that of essence of garlic. 
This peculiarity was well known to the ancients and 
is referred to by Pliny. It was probably the cause of the 
extravagant use of perfumes by the wearers of “the 
purple” in classical times. 
Tilt SOURCES OF THE PURPLE. 
The vague descriptions of the Greek and Latin writers 
has led to much discussion as to the exact species of 
shell-fish used in the manufacture of the dye. 
Pliny speaks of two kinds that produce the purple 
colour. The smaller “fish,” he tells us, was called the 
“buccinum,” from its resemblance to the conch by which 
the sound of the buccinus or trumpet is produced; the 
other “fish” was known as the “ purpura,” or purple, and 
was studded with points up to the very apex, differing in 
this respect from the first kind. 
The earliest attempt to discover the source of the 
ancient purple seems to have been made by William Cole, 
of Bristol, in 1686,* who conducted experiments on shell- 
fish (Purpura lapillus) found on the shores of Somerset- 
*Phil. Trans. Roy. Soc., Lond., xx., pp. 275-—86, and plate. 
