By microscopic examination of the myriads of minute insects which cause
this phenomenon, no other fact has been elicited than that they contain
a fluid which, when squeezed out, leaves a train of light upon the
surface of the water. The creatures appear almost invariably on the eve
of some change of weather, which would lead us to suppose that their
luminous phenomena must be connected with electrical excitation; and of
this Mr. C. Peach of Fowey has furnished the most satisfactory proofs
yet obtained.[13]