ON LUMINOUS Ml&iALS. 



49 



(?ipated by the worm crawling over cold substances. The 

 luminous portion of the tail, when very brilliant, appeared 

 to raise the therraoiBGter more quickly than the other parts 

 of the body, but it was not invariably the case. When 

 shining stroogly, I thought that the luminous rings com- 

 municated the sensation of wanntb to the hand, but thii 

 was probably a deception, as the actual degree of heat was 

 not sufficient for such an effect. It should hpwever be 

 mentioned, that in Templar*a observations ou the glow- 

 worm, he said his feelings deceived him, if he did not ex- 

 perience some heat from the shining of the insect*. 



Exp, 6. To satisfy myself how far the evolution of heat but only -jrhile 

 during the shining of glow-worms depended upon the ]ifg *"^y wtreaii?*. 

 of the animals, I cut off the luminous portion of the tail 

 from several living worms; and 1 found, that, if the thefi- 

 momfeter was applied to them immediately, it was raised by 

 them one or two degrees ; but after these parts were dead, 

 although they continued to emit light, they produced no 

 effect whatever upon the instrument. 



Exp. 7. Some hemispherical medusae w>Fe put into a Medusa shone 

 spoon, containing a small quantity oP seawater, and held wli«n*»-atedin 

 over a burning candie. As soon as the water became heated, * 



the medusoe appeared like illuminated wheels, the spots at 

 the margin and centre alone emitting light; in which man- 

 ner they shone vividly and permanently for about 20 se- 

 conds, when they shrunk and died, after which they were 

 no longer luminous. 



Exp. 3. Some of the same species were put into spirits : immeTsed ia 

 a strong and unremitting light was instantly given out, ^i''"""** 

 which issued from the central tmd marginal parts, a3 in tht 

 preceding experiment, and continued until they died. 



Exp. g. Some of the scintillating and hemispherical ©r shaken in a 

 species of medusa, contained in a small glass jar, were in- 'acuMmi 

 troduced into the receiver of an air pump, and, the air being 

 exhausted, they slione as usual wheij jshaken ; if any differ- 

 ence could be perceived, the light swas more easily excised, 

 and continued longer in vacuo. 



' • Phil. Trans. No. 7-3, 



Vox,. XXVllI.— Jan. ISll. E I wished 



