disk shaped see also fig1 and has an undersurface 156 covered by a conductive material such as copper the second contact element 152 best shown in fig1 comprises a buoyant body 158 which supports a mast 160 of conductive material such as copper the body 158 may be rendered buoyant by forming it of a buoyant material or by shaping it to have an air pocket 159 or both as shown in fig1 which shows the assembled switch 100 in longitudinal cross section the first element 150 is supported inside and near the top of the tubular portion 108 of the body 104 on the upper edge of the sleeve 140 a conductive wire 162 extends from the first element 150 a second conductive wire 164 coils about the mast 160 of the second element 152 the wires 162 and 164 extend down the housing body 104 between the inner wall of the tubular portion 108 and the grooves 144 and 146 of the sleeve 140 as shown in fig1 and 13 the wires 162 and 164 exit the housing through the bore 130 in the bottom 106 see also fig1 the wires 162 and 164 are used to interpose the switch in an electrical circuit and the rest of the system to be described fully below the conductive wires 162 and 164 preferably are 28 gauge teflon coated wiring returning to fig1 it now will be understood that as the level of the fluid 12 rises and falls in the well casing 16 the buoyant second conductive contact element 152 rises and falls more particularly when the switch 100 is not submerged the second contact element 152 rests at the bottom of the tubular portion 108 preventing.