the lagoon for the line of sight between stations. Recommendations. It is recommended that four Bilby portable metal towers of the type used by the U.S. Coast and Geodetic Survey be obtained for use in this survey. These portable towers would reduce the time and expense of tower erection and would considerably reduce the expense involved in prefabricating and shipping wooden towers, Comparative requirements are shown. If Bilby towers are obtainable they can be moved to new locations as observations of portions of the scheme are completed. Higher towers would be practical thereby reducing heights at other stations. The total requirements would be four Bilby portable towers and material for three ten and one fifteen foot wooden tower. If prefabricated wooden towers are used it would not be practical to move them to new locations or to use higher towers. Total requirements would be three twenty~five and two fifteen foot prefabricated towers and instrument tripods, four prefabricated twenty-nine foot instrument tripods and materials for three ten and one fifteen foot wooden tower and tripod. The additional temporary station to be established in the lagoon will require soundings to determine the contour of the bottom and prefabricating a base which can be dropped in place and weighted with sand bags. Observations will be made at night by means of target lights and will follow accepted procedure of the U.S, Coast and Geodetic Survey. Radio com- munication between the observer and light tenders is recommended, but satisfactory communication can be obtained with signal lights. A field calculation of the scheme will be made and sent to the design office for checking. Station markers will be referenced to prevent loss by subsequent operations in the vicinity.