164 
within the opening of the liquid were equal to the tension 
due to the temperature under ordinary circumstances, this 
would be inappreciable. So that unless the tension of 
vapour within small openings were much greater than that 
in larger openings for the same temperature, its effect might 
be neglected; and so far from this being the case, Sir William 
Thomson has shown that the pressure of the vapour within 
a bubble at any particular temperature diminishes with the 
size of the opening. Hence it is clear that this vapour can 
have no effect on the result — a conclusion verified by the 
now well known fact that water may be raised to a tempera- 
ture high above 212° without passing into steam. 
Experimental Verification necessary. 
This line of reasoning has been apparent to me now for seve- 
ral years. I find notes on some of the principal points which I 
made in 1873, and for several years I have pointed out the 
conclusions arrived at as regards the probable cohesion of 
water to the students in the engineering class at Owens 
College. I have, however, hitherto refrained from publishing 
my views, because I had no definite experimental results 
to appeal to in confirmation of them. Experimental indica- 
tions of such a cohesive force were not wanting, but they 
were not definite. And although methods of making definite 
experiments have often occupied my thoughts, certain diffi- 
culties, which turn out to have been somewhat imaginary, 
kept me from trying the experiments. 
It had always appeared to me that in order to subject the 
interior of a liquid mass to tension, it would be necessary 
to, as it were, hold the surface of the liquid at all points to 
prevent its contracting. To accomplish this it was neces- 
sary to have the liquid in a vessel, to the surface of which 
the liquid would adhere as water adheres to glass. The 
experiment which I had conceived would have been equi- 
valent to a vertical glass tube more than 32 feet long, closed 
at the upper end and open at the lower, so that when the 
