VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 639 



living glow-worms were put into a one-ounce phial, with a glass stopple; and 

 though they were perfectly dark at the time, yet, if the phial was briskly rubbed 

 with a silken or linen handkerchief, till it became pretty warm, it seldom failed to 

 make them display their light very finely. This experiment was very frequently 

 repeated. It had the same illuminating effect on the light of a dead glow-worm. — 

 Exper. Q. The complete influence of 212 degrees of heat was now applied to the 

 light of a glow-worm, by pouring on one when dead, but in a luminous state, 

 some boiling water. Its light was instantly extinguished, and did not revive. The 

 experiment was repeated, and with the same result. 



Any of the saline Solutions mentioned in the 4 th Section, being impregnated with 

 luminous matter, and left some time at rest, are rendered more lucid by a mo- 

 derate Degree of Heat. 

 This is proved by 3 different experiments. 



Their Light is extinguished by a great Degree of Heat. 

 This is also proved by 3 separate experiments. The luminous property was 

 destroyed by a degree of heat from q6 to 100. 



If much Heat be applied to the Bottom of a Tube filled with illuminated Liquid, 

 which has been some Time at rest, the Light will descend in luminous Streams, 

 from the Top of the Tube to the Bottom, and be gradually extinguished. 

 Exper. 10*. A glass cylindrical tube, closed at one end, being 9 inches long, 

 with a bore of l^V inch, when used, was put into a gallipot 34- inches deep, and 

 3-|- wide, which held about 12 oz. of boiling water, and was placed in another 

 larger vessel, to receive the overflowing water on the immersion of the tube. The 

 tube being filled over night with some very luminous liquid, was placed in the 

 laboratory till the next evening. The light had then ascended plentifully to the 

 top of the fluid, the rest being dark, and, taking the circular shape of the tube, 

 formed a very lucid ring. The vessels with the boiling-hot water were then carried 

 into the dark laboratory; and the tube being gently and carefully placed, without 

 shaking, in the gallipot, the light was, generally in about -§- a minute, seen plainly 

 to descend in streams from the top to the bottom, illuminating the whole fluid in 

 its descent in a beautiful manner, and then was gradually extinguished. The ex- 

 tinction of the light began at the top of the tube, and ended at the bottom. — 

 Exper. 17. The experiment was also made with a tube 19 inches high, 4- an inch 

 in bore, having several curvatures, and sealed hermetically at its lower end. Both 

 the extremities were made straight for a few inches; the one to be immersed in 

 the water, and the other to prevent the liquid running out. The luminous ring 

 being formed as above-mentioned, the tube was put into the gallipot of boiling-hot 

 water; in a short time the light began to descend from the top, and came waving 

 down, in a pleasing manner, to the bottom of the tube in the hot water, and 

 then was by degrees extinguished. The whole length of the tube, including the 

 curvatures, was 26 inches. 

 The most eligible solutions for this curious experiment, are those made with 



