Conclusions. As a result of the tests made with the six test models, the following conclusions were drawn:

Effective Depths. Effective depths of the unit in the North and Blatic Seas ranged from 65 to 100 feet; along the Atlantic coast (European) 100 to 165 feet; and up to 230 feet in the Mediterranean. Muddy bays and river estuaries are not suitable for these units.

Contemplated Mine Cases. For depths up to 100 feet, the most suitable type of mine shells would be a hemispherical type similar to RMA or a type even flatter. For depths from 100 to 230 feet, a moored mine would be necessary. Since in depths over 100 feet target damage is small, it was contemplated that the moored mine would rise to the sur-face on actuation and the explode. The mechanism to accomplish the release of the mine was to be an explosive device coupled to the mine mooring.

Window Construction and Protection. Safety glass of 3/4 inch thickness capable of withstanding a pressure of 130 pounds per square centimeter was satisfactory for the unit window. The problem of keeping the window clear of marine growth was most diffi-cult. A poisonous lacquer paint was tried. To prevent the paint from coming loose, the smooth surface of the windows was roughened by sand. The binding material in the lac-quer was slightly water-soluble to permit the paint to give off its poisons continuously, the poison selected being arsenic and copper salts. It was found that a paint of this type would last about three months and did not impair the transperency of the window if the lacquer and the glass had the same index of refraction. A desiccator was used to prevent foggin of the window.