638 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



But, by placing the phial in water at about 62 , the glowing property of the insect 

 soon returned. In this experiment, the glow-worm was evidently congealed ; for 

 it adhered to the side of the glass, and was covered with a hoar-frost. This expe- 

 riment was frequently repeated, and with the same result. 



Obser. By these experiments we learn, that cold extinguishes spontaneous light 

 in a temporary manner, but not durably, as the substances of the 3d ^. do ; be- 

 cause the light revived again in its full splendour, as soon as it was exposed to a 

 moderate temperature. 



Section 9. The Effects of Heat on Spontaneous Light. 



The Light of Fishes. — Exper. 1. One side of a luminous herring was held 

 before the fire, for a short space of time, but so as to receive its heat very strongly. 

 It was then conveyed into the laboratory ; when that side which had been exposed 

 to the fire was found quite dark, but the other continued still luminous. The fish 

 was preserved till the next evening, but the extinguished light did not re-appear. — 

 Exper. 2. A whole herring, finely shining, was thrown into a quantity of boiling- 

 hot water, and the light was immediately extinguished: after keeping it there for 

 some time, it was taken out, but the light did not revive. 



The Light of shining Wood. — Exper. 3. A piece of shining wood, its light being 

 very faint, was put into tepid water at about go degrees of temperature, and it 

 became in a short time much more lucid. Another piece, at 96 , was rendered 

 beautifully luminous. — Exper. 4. A pretty thick piece of shining wood was put into 

 a gallipot, and sunk under water by means of a weight, together with a ther- 

 mometer, at the temperature of 64°. Boiling-hot water was then added by spoon- 

 fuls; and the light, at first, was rendered much mere vivid, but soon after began 

 to decrease, and was apparently extinct at about 110°. I say apparently, because 

 on the next evening the light had somewhat revived; which shows, that the heat 

 of 110° was not sufficient to extinguish totally all the light inherent in this piece 

 of wood. — Exper. 5. Finding that 1 10° of heat did not wholly extinguish the light 

 of shining wood, a good many fragments, of different sizes, were then submitted 

 to the power of boiling water, and detained therein for some time, in order that 

 the heat might penetrate them thoroughly. The effect was, that the light became 

 quickly extinct, and did not, as before, re-appear on the following evening. 



The Light of Glow-worms. — Exper. 6. A dead shining glow-worm was put 

 on 2 ounces of water, contained in a wide-mouthed phial, at the temperature of 

 58°. The phial was then sunk, about 2 or 3 inches deep, in boiling-hot water; 

 and, as the heat communicated itself to the contents of the phial, the light of 

 the glow-worm became much more vivid. — Exper. 7 . Another lucid dead glow- 

 worm was put into warm water, at 114°, to see if that degree of heat would ex- 

 tinguish the light; but, on the contrary, its glowing property was augmented. 

 All the water was then poured off, yet the insect continued to shine for some 

 length of time. — Exper. 8. The effect of that heat which is obtained from dry 

 solid bodies by friction, was next tried on the light of the glow-worm. Two 



