Ixviii INTRODUCTION. [CH. 



green when first drawn upon linen, grows a little ruddy 

 afterwards, till it comes to a faint purple ; when dry, 

 and the linen washed, it is of a good purple, and rather 

 betters by age and frequent washing." A cambric 

 handkerchief, which I stained more than twenty years 

 ago with the dye from the purpuriferous gland of a 

 dog-whelk, still retains its violet hue. The pillar lip of 

 this shell often exhibits the same tinge of colour. 

 Nearly two centuries ago Lister tried, but in vain, to 

 fix the purple dye which is yielded in such quantity by 

 the Planorbis corneus, a freshwater snail. 



(Economy.) Other uses to which the shells of Mol- 

 lusca are sometimes applied in this country are numerous 

 and varied, although not very important. The valves 

 of the great pond-mussel (Anodonta cygnea) make here, 

 as well as in the North of France, excellent cream- 

 skimmers. The mussels are procured by means of a 

 long pointed stick, which is inserted between the gaping 

 valves when the animal is feeding, and these closing on 

 the stick allow it to be drawn up out of the water. The 

 shell of the almond- whelk (Fusus antiquus) serves our 

 northern fishermen for a lamp, being suspended from a 

 nail in the wall or ceiling of their hut by a piece of 

 string, which is fastened round the shell in a triangular 

 fashion. The inside is filled with fish-oil, and a wick of 

 cotton or tow is put into the canal at the extremity of 

 the mouth. This I have seen prepared and used in the 

 Shetland Isles ; and I doubt whether any antique lamp 

 could excel it in elegance of shape. In the palmy days 

 of the Italian and Flemish schools, valves of a freshwater 

 mussel (named for this reason Unio pictorum) were used 

 by the great masters to hold their colours. Although 

 they have been superseded by palettes for this purpose, 

 they are sold by many artists'-colourmen in London, 



