on the Light emitted from various Bodies. 183 



discovered ; a proof that all the light had been totally extin- 

 guished by the power of heat. 



If much Heat be applied to the Bottom of a Tube filled with illu- 

 minated 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. 16. A glass cylindrical tube,' closed at one end, being 

 9 inches long, with a bore of l— inch, when used, was put into 

 a gallipot 3^- inches deep, and 3^ wide, which held about 12 

 ounces of boiling water, and was placed in another larger 

 vessel, to receive the overflowing water upon the immersion of 

 the tube. The tube being filled over night with some very lumi- 

 nous liquid, was placed in the laboratory until 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 half 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 extinction 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 10, 

 inches high, ■§ 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 



