NATURAL HISTORY. 



645 



which it lived nearly two hours, 

 and continued to emit light as 

 usual until it died, when the lumi- 

 nous appearance entirely ceased. 



Experiment 2. — The luminous 

 substance was extracted from the 

 before-mentioned glow-worm, and 

 from others killed in different 

 ways, but it aff"orded no light. 



Experiment 3. — The sacs con- 

 taining the luminous matter were 

 cut from the bellies of living glow- 

 worms, and shone uninterruptedly 

 for several hours in the atmos- 

 phere, and after their light became 

 extinct, it was revived by being 

 moistened with water ; some of 

 these were put into water in the 

 first instance, in which they con- 

 tinued to shine unremittingly for 

 forty-eight hours. 



Experiment 4. — The luminous 

 substance of a glow-worm was ex- 

 posed to a degree of heat which 

 would have been sufficient to in- 

 flame phosphorus, without in- 

 creasing the brilliancy of its hght; 

 and farther, it could not be made 

 to burn by being applied to a red- 

 hot iron, or to the flame of a 

 candle. 



• Experiment 5. — A delicate ther- 

 mometer was introduced amongst 

 some living glow-worms during the 

 time they gave out much light: 

 the temperature of the room being 

 69, the instrument rose to 75, 

 76, and 77, according to circum- 

 stances, as the warmth was re- 

 flected from the hand, or dissi- 

 pated by the worm crawling over 

 cold substances. The luminous 

 portion of the tail, when very 

 brilliant, appeared to raise the 

 thermometer more quickly than 

 the other parts of the body, but 

 it was not invariably the case. 

 When shining strongly, I thought 



that the luminous rings commu- 

 nicated the sensation of warmth 

 to the hand ; but this was proba- 

 bly a deception, as the actual de- 

 gree of heat was not sufficient for 

 such an eflvect. It should, how- 

 ever, be mentioned, that in Tem- 

 plar's observations on the glow- 

 worm, he said his feelings de- 

 ceived him, if he did not experi- 

 ence some heat from the shining 

 of the insect. 



Experiment 6. — To satisfy my- 

 self how far the evolution of heat 

 during the shining of glow-worms 

 depended upon the life of the ani- 

 mals, I cut off" the luminous por- 

 tion of the tail from several living 

 worms, and I found that if the 

 thermometer was applied to them 

 immediately, it was raised by 

 them one or two degrees ; but 

 after these parts were dead, al- 

 tliough they continued to emit 

 light, they produced no effect 

 whatever upon the instrufnent. 



Exveriment 7. — Some hemi- 

 spherical medusae were put into a 

 spoon containing a small quantity 

 of sea water, and held over a burn- 

 ing candle. As soon as the water 

 became heated, the medusae ap- 

 peared like illuminated wheels, 

 the spots at the margin and centre 

 alone emitting light ; in which 

 manner they shone vividly and 

 permanently for about 20 seconds, 

 when they shrunk and died, after 

 which they were no longer lumi- 

 nous. 



Experiment 8. — Some of the 

 same species were put into spirits: 

 a strong and unremitting light was 

 instantly given out, which issued 

 from the central and marginal 

 parts, as in the preceding experi- 

 ment, and continued until they 

 died. 



