LIMPET. 49 



If you look carefully over the rocks, especially when 

 these are of a somewhat soft nature, as the slates and 

 shales, you will find oval depressions, sometimes but 

 just discernible, at other times sunk to the depth of an 

 eighth of an inch, corresponding in outline to the shell 

 of a Limpet ; and in many instances you will actually 

 see a Limpet imbedded in such a pit, which it accurately 

 fills. Strange as it may seem, it has been ascertained 

 that these cavities are formed by the animals, which 

 make them their ordinary resting-places, wandering 

 away from them nightly to feed, and returning to them 

 to rest early in the morning. 



The force with which a Limpet adheres to the rock 

 is very great, especially when it has had warning of 

 assault, and has had time to put out its muscular 

 strength. Eeaumur found that a weight of twenty- 

 eight or thirty pounds was required to overcome this 

 adhesive force. His experiments seem to prove, how- 

 ever, that its power is mainly owing, not to muscular 

 energy, nor to the production of a vacuum in the manner 

 of a sucker. If an adhering Limpet were cut quite 

 through perpendicularly, shell and animal, the two 

 parts maintained their hold witli unabated force, al- 

 though of course a vacuum, if there had been one, would 

 have been destroyed by the incision. The power is 

 D 



