Abstract: In a preferred embodiment of the invention, there is provided a laminated vessel wall which is able to enclose electrically conductive liquid with a know electrical property and which vessel laminated wall has alternate electric conductive and non-conductive layers of horizontally-lying whole-circumscribing frame elements lying one stacked on the other, the non-conductive layers being transparent for easier observation of the position of the liquid, and the position of the liquid within the enclosed vessel wall can be determined outside of the vessel wall by using the electrical conductivity of the electric-conductive layer which establishes a closed electrical circuit through the liquid and the vessel wall by directing conducted through a convenient outer measuring mechanism having a sliding contact contactable separate with each of the conductive layers, and this measurement of the position of the liquid being accomplished by the establishment of electrical circuit through the liquid, a conductive layer of