94 KANSAS ACADEMY OF SCIENCE. 



regularly and gradually from the bottom upward. Water introduced into the tube 

 boiled upon reaching the bottom, and the vapor rose slowly until it reached a level pos- 

 sessing a temperature between 60° and 70°, when it condensed. The experiment was 

 repeated many times, under varying conditions, and with different kinds of oil, but 

 always with the same result. 



IV. 



In these experiments it was unfortunately impossible to measure the temperature of 

 the vapor itself. It seems highly improbable that bubbles of steam rising slowly through 

 a meter or more of oil would maintain a temperature thirty degrees above that of the 

 surrounding liquid; and the following considerations, the result of repeated observation, 

 are thought sufficient to show that the difference between the temperature of the vapor 

 and the oil through which it passed was very small: 



1. The bubbles of vapor contracted continually up to the moment of condensation, 

 and as nearly as could be estimated the contraction was such as would have resulted had 

 the bubbles assumed the temperature of the liquid through which they were passing. 



2. The upward velocity of the bubbles varied greatly with the viscosity of the oil, 

 being about 120cm. per second in castor oil, and 200cm. per second in linseed oil; but 

 the apparent temperature of condensation, while it varied somewhat in different oils, 

 being about 62° in castor oil, 67° in olive oil, and 70° in linseed oil, was lowest in the 

 most viscous and highest in the most limpid of these oils. If there had been a great 

 difference of temperature between the vapor and the oil, the apparent temperature of 

 condensation would have been higher in the more viscous oils than in those through 

 which the bubbles of steam rose more rapidly. That is to say, the temperature of the 

 vapor at the time of condensation would be more nearly that of the surrounding oil in 

 the case of viscous oils, because of the longer time for cooling. 



3. The apparent temperature of condensation was not the same throughout the course 

 of an experiment. It was somewhat lower at first when the vapor condensed near the 

 bottom of the tube than when it passed to the top of the tube before liquefying. This 

 would seem to indicate that the vapor did not instantly assume the temperature of the 

 oil through which it was rising; but the apparent temperature of condensation did not 

 vary more than four or five degrees between the bottom and top of a column (a metre 

 long ) of the most viscous of these oils. 



4. Large and small bubbles had the same apparent temperature of condensation. 



5. Steam confined within glass tubes, (below the surface of an oil bath,) as in the 

 first experiment described in this paper, condensed as soon as the bath reached the boil- 

 ing point of water. In this case the apparent temperature of condensation was also the 

 true one, and I believe it may be so considered in all these experiments without serious 

 error. 



The temperature of condensation of super-saturated steam obtained by this method is 

 as far below the boiling point as the temperature of explosive ebullition in Donny's ex- 

 periments and those described in a previous paragraph lie above that point; i. e., about 

 30°. The temperature 70° and 130° are then those of the maximum (C ) and minimum 

 ( E ) of the continuous expansion-curve. The portions B C and E F are plainly deter- 

 minable. Under conditions which permit ebullition after super-heating, the portion 

 D E, as has been pointed out by Maxwell*, cannot be determined; but the experiment 

 with ether in which the liquid did not boil at all, indicates conditions under which the 

 curve is of a determinate character throughout. 



As the boiling point approaches the critical temperature, the maximum and mini- 

 mum become less marked, and finally disappear. Whether the curve at a given pressure 

 varies also with the conditions of the experiment, as Dufour's experiment, in which 



• Clerk Maxwell, Theory of Heat, p. 127. 



