71 



finger, which may be either ascribed to mechanical 

 excitement, or increased temperature. Though no 

 light could be seen by day, the same sea weed, pre- 

 served until the evening, became as brilliant as any 

 other. This last we are inclined to ascribe to the 

 hygrometric state of the atmosphere at this period, 

 and the deliquescent affinity of the saline matter that 

 adhered. The testaceous tenant of the mytilus litho- 

 phagus, or burrowing mussel, is phosphorescent. The 

 fishermen in the bay of Naples are said, sometimes, to 

 place the animal in the sun, and afterwards to rub their 

 hands and face over with the moisture which exudes, 

 by which the skin is rendered luminous ; in this case, 

 solar light, or the heat it imparts, seems to rouse 

 into existence the dormant light of the ova of lumi- 

 nous molluscse, perhaps in this case parasitic. The 

 pholas also emits a phosphorescent light, a phenome- 

 non noticed by the ancients, and recorded by Pliny, 

 who says, that it gives light in the mouth of him that 

 eats it. The fresher it is, the more luminous it be- 

 comes ; and when dry, it may be revived, by the ap- 

 plication of either salt or fresh water. Spirit destroys 

 it, also acids ; caustic potassa and muriate of am- 

 monia exceedingly reduce its phosphorescence : milk 

 is rendered luminous by it ; this ceases by the addi- 

 tion of sulphuric acid, but potassa revives it, ap- 

 parently by neutralising the acid. It is stated, that 

 a single pholas (pholas dactylus ? ) renders seven 

 ounces of milk so luminous, that surrounding objects 

 are rendered visible by it, and the presence of atmo- 

 spheric air is said to be necessary. When the pholas 

 was preserved in honey, it maintained its luminous 

 character for more than twelve months, and the light 

 could be evolved at pleasure by the application of 

 warm water. 



