Abstract: An ice island is constructed in a marine area having a sheet of natural ice whereby, in a basic embodiment, a lower layer of fresh water ice is made by continually adding fresh water to the ice sheet and letting it freeze until the sheet is on bottom. An impervious insulating layer is put on top of the fresh ice and an upper layer is constructed thereon from sea water or mined ice blocks.

Abstract: An ice island is constructed in a marine area having a sheet of natural ice by mining ice blocks from the ice sheet, curing the blocks and placing the cured blocks directly on the ice sheet until the natural sheet touches bottom and the desired weight of the ice island is obtained. Methods are disclosed for special placement of the blocks to prevent overstressing the natural ice sheet.

Abstract: A cylindrical stress sensor has a case that is long relative to its diameter. The case may be completely imbedded in the body of a host material in which a change of stress is of interest. That portion of the sensor which is imbedded has a rounded end. The rounded end, circular cross section, and relatively large length-to-diameter ratio avoid errors occasioned by stress concentration. A strain transducer of a vibrating wire excited by a magnetic coil is located remote from any imbedded end of the sensor. Changes in strain on the wire alter the frequency of the wire. This change in frequency is picked up by the excitation coil as a signal. A stacked, three-transducer array, with the wire of each transducer at 45.degree. from a neighboring transducer, can detect changes in the magnitudes and directions of the principal stresses, without first establishing the direction of the primary or secondary principal stress.