2 9 6 D O C . 2 9 3 O N C E N T E N A R Y O F K E L V I N
foundations of physics began, the end of which still cannot be foreseen today.
Thomson, to whom the ultimate foundations of physical knowledge seemed secure
nearly to the end of his life, would shudder if he could take an unprepared glance
at our current scientific literature.
Instead of making an attempt to give an overview of Thomson’s lifework, I pre-
fer to show the acumen of his inventive mind with a couple of simple examples that
appealed to me particularly.
The water-drop apparatus for the generation of electrostatic
charges:[2]
Two streams of water trickle out of the buried water-supply pipe R, breaking
apart into drops in the interior of the isolated metal hollow cylinders C, C′ and fall
into the isolated props A, A′, fitted inside with funnels. C is electrically connected
with A′, C′, and A. When C is positively charged, the drops formed inside C become
negatively charged and pass their negative charge on to A, charging C′ negatively
at the same time.
1. Water-drop apparatus for the
generation of electrostatic charges.
2. Influence on vapor tension of a
liquid surface’s capillary curva-
ture.
Figure 1. Figure 2.
As a consequence of the negative charge of C′, the water drops forming inside C′
become positively charged and discharge inside A′, increasing the positive charge
of A′ and C. The charging of C, A′ and C′ A thus rises as long as the insulation pre-
vents a compensatory spark.
The influence of a liquid surface’s capillary curvature on vapor
tension:[3]
The little capillary tube (inner radius R) is dipped, e.g., inside a nonwetting liq-
uid. Inside the tube, at equilibrium, there is a capillary depression in the amount of
[4]
If denotes the vapor’s density (small compared to ρ), then compared to the
free liquid, at the meniscus there is an overpressure in the amount of
[p. 602]
h
2σ
Rρg
---------- =
σ capillary constant =
ρ liquid density =
g gravitational acceleration¹ = ©
¨ ¸
¨ ¸
§ ·
ρ0
Δp ρ0gh
2
R
-----------.0σρ
ρ
= =