Abstract: A system including a source of electrical energy, a transformer, a plurality of submerged tanks, each having a perforated container therein, a first multiple switch electrically connected to the transformer, a plurality of conductors, each selectively leading from the first multiple switch to a first conductor in each perforated container in each tank, a second electrical conductor arranged in each perforated container in each tank, a float formed of insulating material arranged in each perforated container in each tank which float is guided vertically by the conductors in the perforated container and each of which has an electrical contact secured to its upper portion which engages the conductors in each perforated container, an electrical conductor connected to the second conductor in each perforated container, each of which leads to a second multiple switch and each of which is capable of being selectively connected by the second multiple switch to the coil of a galvanometer which moves a pointer connected