94 Mr. C. Tomlinson on some Phenomena 



In asking my friend Mr. Hatcher to continue these experi- 

 ments, I suggested the following particulars : — If the oil-bath 

 were kept at a pretty steady high temperature, the results of 

 the experiments would be more comparable. In the selection of 

 tubes, avoid those that contain nuclear specks, which become 

 evident when a liquid is boiled in a tube over the flame of a 

 spirit-lamp by the stream of bubbles that escapes from one or 

 two points. The results would also be more satisfactory if the 

 tube were sustained in a vertical position in the bath. When 

 inclined there is a shallow depth of liquid at the elongated ellip- 

 tical surface, on which the heat acts more easily than on greater 

 depths. The tube should not touch the bottom of the oil-bath ; 

 for there the temperature is higher than just above. The thermo- 

 meter in the tube must be quite clean. If the scale on the stem is 

 filled in with black, this, being a mixture of lampblack and grease, 

 is nuclear. The thermometer should not touch the bottom of 

 the tube, because, if it does, a thin capillary film of liquid is formed 

 beneath it, which readily bursts into vapour. If the rounded 

 end of a glass rod or the thermometer- bulb be held against the 

 bottom or side of the vessel containing a boiling liquid, a rapid 

 stream of bubbles escapes from the point of contact. Nor should 

 the thermometer-stem touch the side of the tube, for the same 

 reason, but be suspended in its axis so as to be read easily with- 

 out disturbing the liquid. Mechanical holders are useful in ex- 

 periments of this kind. 



The following results were obtained, subject, as nearly as pos- 

 sible, to the above conditions. The thermometer had an exte- 

 terior casing tube. The tube used in boiling (except in one 

 experiment) was about \\ inch in diameter; and the thermo- 

 meter was suspended freely within it with the bulb at about 

 half the depth of the water. The difference in temperature 

 between the bath and the water was maintained at about 60° F. 

 until the water first boiled, when the temperature was allowed 

 to rise. 



Experiment 5.— A 1-inch tube used, but> being rather too 

 narrow for the cased thermometer, was not employed again. 



Bath 275 Water 208. First bubble of steam. 



216. Boiling briskly; a sudden burst of 

 vapour caused the temperature to 

 fall. 

 300 222. Burst of vapour, and fall to 



216. 

 300 224. Burst, and fall to 



217. 

 300 230. Burst of vapour, and the whole of the 



water was blown out of the tube. 



