THE PINNA AND THE MUSSEL. 



pared with an equal bulk of water — is so great, that when 

 submerged, it falls into a sort of arch-like form, and so attains 

 an elasticity which takes off much of the strain on the anchor, 

 and protects it from dragging. 



We will now look to Nature for Cables. 

 The natural cable which will first suggest itself is evidently 

 that of the Pinna Shell (Pinna pectinata), which fixes its shell 



EGG OF DOG-FISH. 



PINNA. 

 WATER-SNAIL ANCHORED 

 TO WATER-LILY LEAF. 



ANCHORED BOAT. 



to some rock or stone with a number of silk-like threads, spun 

 by itself, and protruding from the base, just as a vessel on a 

 lee shore throws out a number of cables. The threads which 

 compose the " byssus," as it is called, are only a few inches in 

 length, and apparently slight. They are, however, really 

 strong, and by acting in unison enable the shell, though some- 

 times two feet in length, to be held firmly to the rock. I may 

 here mention that they have been occasionally woven into 

 gloves, and other articles of apparel, to which their natural 

 soft grey-brown hue gives a very pleasing appearance. 



A still more familiar instance of a natural marine cable is 

 given by the common Mussel, which can be found in thousands 

 on almost every solid substance which affords it a hold. Even 

 copper-bottomed ships are often covered with Mussels, all 

 clinging by their natural cables, and it is thought that the 

 cases which sometimes occur of being poisoned by eating 

 Mussels, or ' ' musselled," as the malady is called by the sea- 

 faring population, are due to the fact that the Mussels have 



P 2 



