INTERNAL COHESION OF LIQUIDS. 15 



suspended as before, for a few seconds only. The tube was 

 then placed in a position with the closed end lowest, so that 

 the air and water might ascend towards the end and pass 

 out ; and after being in this position for some hours, when 

 it was again erected the column remained intact. 



It was thereupon again lowered and left to drain for 

 forty-eight hours. On being again erected, the mercury 

 was still suspended. The tube has since been carried in a 

 more or less horizontal position some three miles to the 

 Society ^s rooms in order that I might exhibit this pheno- 

 menon. If it has not been affected by the shaking, you 

 will see a suspended column of mercury some fifty-nine 

 inches high, or twenty-nine inches above the height due to 

 the atmosphere*. 



Conclusion. 



The difficulty of obtaining a column of mercury thirty 

 inches above the pressure of the atmosphere does not, I 

 think, prove that the limit of the cohesive power of the 

 liquid has been arrived at, or even the limit of the adhesive 

 power of the water for glass and mercury, but simply 

 shows that, although imperceptible, there are still bubbles 

 of air in the liquid between the mercury and the glass 

 which will not readily pass out. 



It seems to me to be probable that, with sufficient care, 

 or by using apparatus more suitable to the purpose, much 

 greater heights might be attained. But however this may 

 be, we have proof that mercury and water will, by their 

 cohesion, resist a tension of at least one atmosphere, or 

 that the common pump would, if the Avater were free from 



* At the Meeting not only did the mercury remain suspended when the 

 tube was erect, but on the pressure of the atmosphere being removed w-ith 

 an air-pump it still remained suspended, although the tension at the top of 

 the tube was nearly equal to two atmospheres. 



