No doubt this explanation is correct so far as it goes, but it is highly probable that when the floating substance dissolves, other forces are called into action in addition to the tensions.
"Liquid Drops and Globules, their Formation and Movements"
Chas. R. Darling
The surface tension of the water, acting horizontally, tends to stretch the globule, and is successful momentarily in overcoming the opposing tensions, each of which pulls at an angle to the surface.
"Liquid Drops and Globules, their Formation and Movements"
Chas. R. Darling
Enlargement of the upper surface of the globule, however, reduces the angles at which the tensions B and C act, and in consequence their effective strength is increased.
"Liquid Drops and Globules, their Formation and Movements"
Chas. R. Darling