Ch. XXIII.] CATEG0EIE8 OF LUMINOSITY. 393 



rally, and at the same time very loosely applied by most 

 observers, but which has no right to any place in the de- 

 scriptions of luminous phenomena as exhibited by the 

 sea. Phosphorescence is here a misnomer, and an even 

 greater misuse of terms is it to speak of phosphorescent 

 matter. There is no phosphorus in the case, nor any- 

 thing allied to it, except ia the abstract meaning of the 

 word; neither is there any combustion; but the Hght is, 

 sui generis, the product of causes of an entirely different 

 category from those which have to do with the light-pro- 

 ducing properties of phosphorus. Nor is the light of a 

 material character, such as could be spread upon the end 

 of a match, like phosphorus; and although in some few 

 cases the luminosity has appeared to cleave to extraneous 

 substances, there can be little doubt that in such cases 

 the light had a different origin, and was of a different 

 character from the ordinary forms of animal luminosity 

 exhibited in living organized bodies. 



But we will first state the facts, and draw some conclu- 

 sions afterwards. And it will make the subject clearer if 

 we follow a methodical arrangement, and group the facts in 

 an orderly manner. I would therefore classify all the cases 

 of luminosity which have come under my observation, under 

 the following five heads : — 



1. Sparks, or points of light. 



2. A soft liquid, general and wide-spread effulgence. 



3. Moon-shaped patches of steady Hght. 



4. Instantaneous recurrent flashes. 



5. Milky sea. 



The first of these, or the appearance of points or sparks 

 of Hght, is by far the most common, and in different degrees 

 may be said to be all but universal. Whether the other 



