"EFFECTS OF HEAT ON FLUIDS, 423 



In these experiments there was no pure boiling of water, 

 i.e. no rupture of cohesion of the molecules of water itself, but 

 the water was boiled, to use M. Donny's expression, by eva- 

 poration against a surface of gas. 



It is hardly conceivable that air could penetrate through 

 such a column of oil, the more so as the oil did not perceptibly 

 absorb the nitrogen freed by the boiling water and resting in 

 the bend of the tube ; but to meet this conjectural difficulty, 

 the following experiment was made : A tube, one foot long and 

 T %ths inch internal diameter, bent into a slight obtuse angle, 

 had a bulb of f inch diameter blown on it at the angle ; this 

 angle was about three inches from one end and nine from 

 the other ; a loop of platinum wire was sealed into the 

 shorter leg, and the whole tube and bulb filled with and 

 immersed into mercury ; water, distilled and purged of air as 

 before, was allowed to fill the short leg, and by carefully ad- 

 justing the inclination, the water could be boiled so as to allow 

 bubbles to ascend into the bulb and displace the mercury. 

 The effect was the same as with the oil experiment, no 

 ebullition without leaving a bead of gas, the gas collected 

 in the bulb, and was cut off by what may be termed a 

 valve of mercury, from the boiling water, then allowed to 

 escape, and so on ; the experiment was continued for many 

 days, and the bubbles analysed from time to time ; they 

 proved, as before, to be nitrogen, and, as before, continued 

 indefinitely. 



A similar experiment was made without the platinum 

 wire, and though, from the greater difficulties, the experiment 

 was not so satisfactory, the result was the same. 



As the mercury of the common barometer will keep air 

 out of its vacuum for years, if not for centuries, there could 

 be no absorption here from the external atmosphere, and I 

 think I am fairly entitled to conclude from the above experi- 

 ments which I believe went far beyond any that have been 

 recorded that no one has yet seen the phenomenon of pure 

 waterboiling, I .^ToTthe disruption of the liquid particles of 

 the" oxyhydrogen compound, so as to produce vapour which 

 will, when condensed, become water, leaving no permanent 

 gas. Possibly, in my experiment of the decomposition of 



