20^! 



Professor Sir James Dewar 



[Jan. 19, 



contraction curve. By dividing the total daily drainage rate given 

 by the slope of the tangent TT', by the corresponding surface at that 

 time, there results the rate of condensation per unit area. The 

 values thus accruing are set out in the first three horizontal rows of 

 Table 12, with the corresponding day in the fourth row : — 



Table 12. 



Daily rate of conden-|Q.Q^gQ.Q3^Q.Q-,^,,gQ.QQgggQ.QQg^Q.QQ^^Q.QQg-^Q.QQ^g 

 sation . . . . j 



153-9 



0-097 



70 



Surface 1353 346-3 333-3 314-2 283-5 254-5 227-0 



i ' i 



Kate per unit area X 10*1 13-9 0-895 0-534 0*282 0-226 0-185 0-187 



Dav 4 8 14 22 33 43 52 



By plotting the third and fourth rows as ordinate and abscissa, 

 a new and more fundamental curve is obtained, which is shown in 

 Fig. 14. 



An examination of this curve shows that the alteration of the 

 rate of condensation on unit area of the bubble after the fourth day 

 is practically hyperbolic as regards time. The expression most nearly 

 fitting the curve is found (by plotting the results logarithmically) to 

 be xy = 0'705, where x represents the time in days and y the 

 milligrammes of condensation on each square centimetre. Calculated 

 points are marked " x " on the diagram, and values obtained from 

 observations as above are marked " 0." 



By bursting bubbles in a weighed vessel, it was found that at 

 the mean thickness which these bubbles maintain under the given 

 conditions (shown by their colour) they haye a weight of very 

 approximately • 1 mgm. per square cm., and are therefore • 001 mm. 

 thick. Hence, in the equation just given, y may also represent 

 the weight (in milligrammes) condensed per day on each 0*1 mgm. 

 of the bubble. The resulting values calculated for certain days are 

 set out in the following Table 16^ together mih. the corresponding 

 values obtained directly from the tangents to the original contraction 

 curve : — 



Table 13. 



dayi 



10 



^co~nd"So'nV'^^^^^^^^^^-^^^^"^^'^-^'^^-^^^ 



gubbTe'"-1^^--^- 



lO- 180 0-088 



14 



0-050 

 0-058 



22 33 43 52 7 



0-0320-0210-01600140-( 

 0-02800230-0190014O-( 



